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SYSTEMATIC    ORGANIC  CHEMISTRY 

MODERN  METHODS  OF  PREPARATION 
AND  ESTIMATION 


/ 


SYSTEMATIC  ORGANIC 
CHEMISTRY 


MODERN  METHODS  OF  PREPARATION 
AND  ESTIMATION 

BY 

WILLIAM  M.  CUMMING  B.Sc,  F.l.C. 

Lecturer  on  Organic  Chemistry  in  The  Royal  Technical  College 
Glasgow  ;  late  of  British  Dyestuffs  Corporation,  Ltd. 

I.  VANCE  HOPPER  B.Sc,  A.R.C.Sc.I.,  F.l.C. 

Lecturer  on  Organic  Chemistry  in  The  Royal  Technical  College^ 
Glasgow  ;  late  of  British  Dyestuffs  Corporation,  Ltd. 

AND 

T.  SHERLOCK  WHEELER  B.Sc,  A.R.C.Sc.I,  A.l.C. 

Chemist,  Research  Department,  Royal  Arsenal,  Woolwich  ;  late  of 
The  Royal  Technical  College,  Glasgow. 

*  *     1     D  to 

■■>        t    1    3  1 


NEW  YORK 
D.  VAN  NOSTRAND  COMPANY 
EIGHT  WARREN  STREET 

1926 

86395 


PRINTED  IN  GREAT  BRITAIN  Rv  m 


PREFACE 

The  present  work  is  intended  as  a  complete  laboratory  guide  to  the 
preparations  and  estimations  of  organic  chemistry  for  undergraduate 
and  post-graduate  students. '  An  endeavour  has  been  made  to  introduce 
J  up-to-date  methods,  some  of  which  are.  new,  having  been  developed  by 
j  the  authors.    In  all  cases  sufficient  practical  details  are  given  to  enable  a 
o  beginner,  with  the  aid  of  the  sections  on  apparatus  and  methods,  to  carry 
out  the  necessary  operations  for  himself.    The  research  student,  it  is 
hoped,  will  often  find  within,  the  preparations  required.    To  meet  the 
needs  of  the  many  students  whose  ultimate  interests  are  likely  to  be 
industrial,  several  manufacturing  methods  are  described  on  a  laboratory 
scale.    An  industrial  experience  which  has  been  invaluable  to  the  authors 
in  their  duties  as  teachers,  has  led  them  to  include  a  few  notes  on  costing, 
since  they  feel  that  this  subject,  of  such  vital  importance  in  industry,  is 
neglected  in  our  technical  institutions. 
^    References  to  the  original  literature  have  been  given  after  almost  every 
^  preparation,  thus  affording  a  means  of  amplifying,  if  desired,  the  practical 
^details.    Stress  has  been  laid  on  the  value  of  consulting  original  papers 
through  the  media  of  the  lexicons  of  Bichter,  Beilstein  and  Stelzner. 

Lists  of  suggested  preparations  have  been  included.  It  is  believed 
that  greater  interest  is  developed  when  the  student  works  through  a 
a  sequence  of  preparations  which  are  more  or  less  intimately  connected. 
*L  The  authors  have  striven  to  make  the  book  something  more  than  a 
^  collection  of  recipes.  Owing  to  deficiencies  in  the  teaching  of  the  subject, 
there  is  to:day  a  tendency  for  the  student  to  think  that  there  is  a  lecture- 
room  and  a  laboratory  variety  of  organic  chemistry.  To  such  an  extent 
does  this  division  exist  that  a  student  who  in  the  lecture-room  knows  the 
general  method  for  the  preparation  of,  say,  anhydrides,  in  the  laboratory 
is  quite  at  sea  when  asked  to  prepare  any  anhydride  other  than  that  of 
acetic  acid.  To  combat  this,  the  preparations  of  several  compounds  of  a 
^  given  type  have  been  included  in  most  sections  of  the  book. 

Many  reactions  of  purely  theoretical  interest  have  been  incorporated, 
so  that  the  student  may  gain  some  real  idea  of  the  possibilities  of  his 
subject,  and  that  he  may  feel  his  practical  and  theoretical  text-books 
to  be  very  near  akin.  Indeed,  the  authors  trust  that  from  a  theoretical 
standpoint  alone  the  student  may  find  the  book  useful  in  that  it  will 
enable  him  to  view  his  subject  from  an  angle  different  to  the  usual,  and 
in  this  way  to  gain  perspective.  The  better  to  accomplish  this,  they 
have  introduced  a  new  classification  of  organic  reactions  in  which  reaction 
follows  reaction  on  a  definite  plan.  They  hope  that  the  student  who 
carefully  reads  through  this  book  will  not  only  have  acquired  much  varied 


vi 


PREFACE 


theoretical  and  practical  knowledge,  but  also  that  his  purely  theoretical 
books  will  take  on  a  new  meaning,  and  that  even  their  current  jargon  of 
"  reducing  A  with  HI  "  and  "  distilling  B  with  lime  "  will  be  for  him  ) 
something  more  than  a  form  of  words. 

Identifications  have  not  been  dealt  with  beyond  including  some  few 
tests  and  tables  of  reactions.  A  section  has  been  included  dealing  with 
the  preparation  of  such  inorganic  compounds  as  are  largely  used  in 
organic  chemistry,  and  on  the  correct  preparation  of  which  much  may 
depend.  The  authors  would  here  emphasise  th  e  importance  of  introducing 
"oleum"  of  all  strengths  into  the  teaching  laboratories  of  this  country. 
It  is  of  great  industrial  importance,  cheap,  and  not  dangerous  when 
properly  handled. 

The  section  on  estimations  is  rather  more  comprehensive  than  is  given 
in  most  text-books  of  this  kind,  and  is  composed  entirely  of  examples 
found  to  give  good  results  in  practice. 

The  authors  beg  to  acknowledge  assistance  received  directly  and 
indirectly  from  well-known  text-books  by  the  following  authors — Adams  \ 
and  others,  Barnett,  Barrowcliff  and  Carr,  Cain,  Cain  and  Thorpe,  Cohen, 
Elbs,  Fiertz-David,  Fischer,  Grattermann,  Henderson,  Knecht  and  Hibbert, 
Lassar-Cohn,  Hans  Meyer,  Meyer- Jacobson,  Meyer-Tingle,  Perkin  F.  M., 
Sudborough  and  James,  and  Ullmann. 

They  wish  to  express  their  thanks  to  Professor  F.  J.  Wilson  ior  his 
kindly  interest  and  valuable  suggestions  ;  to  Professor  I.  M.  Heilbron 
for  useful  advice  ;  to  Mr.  A.  B.  Crawford,  B.Sc.,  A.R.T.C.,  A.I.C.,  and 
Mr.  E.  C.  Pickering,  B.Sc,  A.I.C.,  for  reading  the  proofs  ;  and  to  Messrs. 
Constable  &  Co.  for  the  way  in  which  they  have  carried  out  their  share 
of  the  work. 

They  desire  to  acknowledge  specially  the  assistance  rendered  by  Mr.  , 
James  Connell,  B.Sc,  A.I.C.,  in  drawing  the  illustrations  for  the  book. 

The  authors  will  be  grateful  for  any  suggestions  or  for  notification  of 
any  errors. 

The  Royal  Technical  College,  Glasgow.  W.  M.  C.  AND  I.  V.  H. 

Research  Department,  Royal  Arsenal,  T.  S.  W. 

Woolwich. 


! 


ABBREVIATIONS 


A. 

T  ,ipnirr  «   Atitiq  lfn  r I  or*  t  homi'o 
-LiltJUlg  b  -rillllcLlcIl  U-ci  V^IltJIIlltJ. 

A.  Spl. 

Ssn t^t^I pm on "f"     T  ,i d Ki rr  a    A  nriQ  Ion   r1or»  Pnomm 

oupjjitjiutJiiu,  xjifDuiQ  b  i^.iiiiciit;ii  u.(3i  v^neiiiie. 

A.  Ch. 

a  nn£i  ma  rip  ^Viotyiio  ot-  T-^Vn7CJir*no 
xxllXlctltJo  Lit?  VyllcIIllt?  t?L  Jt  Iiy  biqUt?. 

A  m  Sr*r* 

Journal  of  the  American  Chemical  Society. 

B. 

JL>C-1  l^llLO              JL/tJU.  LoOlltJIl  dltJJlllbL-IltJll  V^Ubt;llbCIl<*l  L. 

B.P. 

"Roilinor  T^riin'f" 

Bi.  '. 

rvfi  1  Ifvtii  n  Hp  1^,  SsriPipf",p  pniminnp  hp  "Paimo. 

C. 

fIVi pm iqpVi pa  f  Ipti t~t*£1  1  nl a  T"f 
WlidllibOIlcb  v^t>ll LI  ct  l  U let  it, 

C.  N. 

Chemical  News. 

C.  r.  '. 

Comptes  rendus  de  l'-Academie  des  Sciences. 

C.  T. 

(IVi omi P£i  1  rF1T'Qflp  .T<~»n i*n ti  1 

d  z.    !  ! 

Chemiker  Zeitung. 

D. 

SsTIPPlri  P    (nrT*£l  VI 

kj  L/C'V^J.IH-'    V^ld  V  11  y  • 

D.R.P. 

nprmfln  T-^si+pn'f 
V.7 Ul  illctll  JT  d  L/Ollt. 

E.P. 

"Rti^igIi  Pafprrl" 

JJIIUOU   X  dlClll, 

F.P. 

G. 

V-TdZjiiCLtaj  dllllllL-ct  1  Lctllctllct. 

J. 

.Ta  Tirp^lipriplif,  Hpt*  plnpmip 

J.  c.  s. 

OOU.Lli.cli.  VI  tilt?  v^lltulllbcll  QOCloty. 

J.  Eng. 

UOUIllctl  Ol  XIllAUbLllctl  dllU.  XLill^lllct^lllli^  V^IlcIIllb  LI  V  • 

J.  pr. 

T    T?    P  Q 

U.   JLV.   V/.  o. 

O  OUIIlctl  Ol  LIlc  XvUbblctll  vyllt?11110<ll  QUOloiy. 

T  S  n  T 

TaiittiqI  at  Ihp  S/~\pi ~\t  r\T  Phptyiipq  I  TnnnafTv 

oouiiicti  oi  tut;  oociuty  oi  v^iitJiiiiocti  j-iiu.ubtiy . 

J.  Soc.  Dyers  . 

Journal  of  the  Society  of  Dyers  and  Colorists. 

M. 

Monatshefte  f iir  chemie. 

M.P. 

Melting  Point. 

P.  A.  . 

Poggandorf  s  Annalen. 

P.  C.  S.  . 

Proceedings  of  the  Chemical  Society. 

P.  R.  S. 

Proceedings  of  the  Royal  Society. 

Phil.  Mag. 

Magazine  of  the  Philosophical  Society  (London). 

Rec. 

Recueil  des  travaux  chimiques  des  Pays  Bas. 

T.  R.  S.  E. 

Transactions  of  the  Royal  Society  of  Edinburgh. 

U.S.P.  . 

United  States  Patent. 

Z.  a. 

Zeitschrift  fur  angewandte  Chemie. 

Z.  Anal. 

Zeitschrift  fur  analytsche  Chemie. 

Z.  Ch.  . 

Zeitschrift  fur  Chemie. 

Z.  e. 

Zeitschrift  fur  Electrochemie. 

Z.  ph.  . 

Zeitschrift  fur  physikalische  Chemie. 

vii 


CONTENTS 

X  PAGE 

Abbreviations      .        .        .        .        .  .        .        .  vii 

PART  I 
CHAPTER  I 

Cautions      ........       ...  1 

^  Scheme  of  Arrangement  of  Reactions       .....  2 

Hints  to  Students      .........  3 

Use  of  the  Library    .        .        .        .        .        .  .  .3 

Suggested  Lists  of  Preparations       ......  4 

Note  on  Costing  .       .       ....              .       .       .  5 

CHAPTER  II 
Apparatus  and  Methods 

Practical  Hints  .        .       .        .       .       .        .       .       .       .  7 

Softening  of  Corks    .        .        .        .        .        .        .        .        .  7 

Boring  of  Corks       .........  7 

Removing  Fixed  Stoppers ........  7 

Crystallisation   .        .        .       .        .        .       ..       .       .  .7 

Crystallisation  by  Cooling         .......  8 

Selection  of  Solvent  .        .        .        .        .        .        .        .        .  8 

Preparation  of  Sohition     ........  9 

\\         Filtration  of  Hot  Solution .        .        ...        .        .        .        .  9 

Cooling  Mixtures      .        .        .        .        .        .        .        .  .10 

Separation  of  Crystals       .        .        .        .        .        .        .  .11 

Crystallisation  by  Evaporation  .        .        .        .        .        .  .11 

Special  Methods  12 

Fractional  Crystallisation         .        .        .        .        .        .        .  12 

Diagrammatic  Representation  and  Explanation  .        .        .        .  13 

Determination  of  Melting  Point        .        .        .        .        .  .15 

Correction       .        .        .  .        .        .  17 

Some  Corrected  Melting  Points  for  Standardising  Thermometers   .  17 

"  Mixed  "  Melting  Points  17 

Setting  Point  .  17 

Distillation  and  Determination  of  Boiling  Point     ...  18 
Corrections      ..........  20 

Some  corrected  Boiling  Points  for  Standardising  Thermometers     .  20 
Fractional  Distillation      .  .        .        .        .        .  .20 

Constant  Boiling  Mixtures         .......  22 

l  Steam  Distillation      .        .        .        .        .....  22 

With  Superheated  Steam  .        .        .  .        .  .23 

Continuous  Steam  Distillation   .        .        .        .        .       ' .  .24 

"  Dry  Distillation  .        .        .        .        .        .        .        .        .  .24 

Vacuum  Distillation    .........  24 

rv         Pumps    .        .        .        .        .        .        .        .        .  .27 

A  Receiver  for  Distillation  in  a  Current  of  Gas  or  under  reduced 

pressure    .        .        .        .        .        .        .        .        .  .27 

ix 


x  CONTENTS 

P/NOE 

Sublimation         .       .       .       .  .       .       .       .  .28 

Filtration    .        .       \        .  .        .        ...        .      28  , 

Decolorising       .       .       .        .        .       .       .  .  30  ' 

Salting  Out        .       .       .       ...       .       .  30 

Extraction  of  Solids  .        .        .        .        .        .        .        .  .31 

Separation  of  Two  Immiscible  Liquids       .        .        .        .  .31 

Separation  by  Extraction  ........  32 

Notes  on  Extraction  with  Ether         .        .        .        .        .  32  . 

Drying         .        .        .        .        .        .        .        .        .  .33 

Drying  of  Solids       .  33 

Drying  of  Liquids    .        .        .        .        .        .        .        .        .      34  -4 

Baths  \        .        .        .        .        .        .        .        .  .  .35 

Mechanical  Agitation         ........  37 

Sulphonation  Pot     .        .        .        .        .        .        .        .  38  ! 

Heating  under  Pressure     .        .        .        .        .  '  .  .38 

Sealed  Tubes  38 

Autoclaves      .  .  .        .        .        .        .  42  4 

Density  of  Liquids      .........  43 

Polarimeter         .        .        .        .        .        ...        .  .44 

Apparatus  for  Certain  Catalytic  Preparations  .  .  .46 
Addition  Tube     .        .        .        .        .        .        .        .  .47 


PART  II 

THE  LINKING  OF  CARBON  TO  CARBON 
CHAPTER  III 
Hydrogen  Compounds 


Reaction  I. — Passage  of  the  Vapours  of  certain  Hydrocarbons  through 

a  red-hot  Tube  48 

Reaction  II. — Reduction  under  certain  Conditions  of  Aromatic  Ketones  50 

Reaction  III. — Oxidation  under  certain  Conditions  of  Lower  Hydro- 
carbons   ..........  50 

Reaction  IV. — (a)  Action  of  Dehydrating  Agents  on  a  Mixture  of  an 

Aromatic  Hydrocarbon  and  an  Aromatic  Alcohol  .  52 
(b)  Action  of  Dehydrating  Agents  on  certain  Ketones  ...  53 

Reaction  V. — Cinnamic  Condensation  and  Elimination  of  Carbon 

Dioxide    .  .        .        .        .        .        .        .  .54 


Reaction  VI. — {a)  Action  of  certain  Anhydrous  Metallic  Halides  on  a 
Mixture  of  an  Aromatic  Hydrocarbon  and  an  Alkyl  Halide 

(Friedel-Crafts)   54 

(5)  Action  under  certain  Conditions  of  Aluminium  and  Mercuric 
Chloride  on  a  Mixture  of  an  Aromatic  Hydrocarbon  and  an 
Alky]  Halide     .  .  56 

(c)  Action  of  the  Aluminium -Mercury  Couple,  or  of  certain  finely 

divided  Metals  on  a  Mixture  of  an  Aromatic  Hydrocarbon 

and  an  Alkyl  Halide  ........  58 

(d)  Action  of  Anhydrous  Aluminium  Chloride  on  a  Mixture  of  an 

Aromatic  Hydrocarbon  and  a  Diazonium  Compound  .  .58 
Reaction  VII. — (a)  Action  of  Sodium  on  Halogen  Compounds  .  .  58 
(b)  Action  of  Metals  other  than  Sodium  on  Iodo-compounds  .  60 
Reaction  VIII. — Action  of  certain  finely  divided  Metals  on  Diazonium 

Compounds  in  Alcoholic  or  Acetic  Anhydride  Solution   .        .  61 


CONTENTS 


xi 


Eeaction  IX. — (a)  Action  of  Magnesium  Alkyl  or  Ary]  Halide  on 
certain  Alkyl  or  Aryl  Halides  in  the  presence  of  Absolute  Ether 

(Grignard)         .        .        .  61 

(/>)  Action  of  Heat  on  the  Compound  formed  by  treating  Grignard 

Reagent  with  a  Ketone  in  absolute  Ethereal  -Solution   .        .  62 
(c)  Action  of  Dimethyl  Sulphate  on  Magnesium  Alkyl  or  Aryl 

Halide  (Grignard)      .        .        .        .        .        .  .63 

|    Reaction  X. — Action  of  Zinc  Alkyl  on  Alkyl  Halides        ...  64 


CHAPTER  IV 
Hydroxy  Compounds 

Reaction  XI. — Intramolecular  Elimination  of  Water  from  certain 

Molecules  ..........  65 

Reaction  XII. — Reduction  of  Aldehydes  and  Ketones  to  Pinacones  .  65 
Reaction  XIII. — Condensation  of  a  Phenol  with  Formaldehyde  .  .  66 
Reaction  XIV. — (a)  Action  of  Magnesium  Alkyl  or  Aryl  Halide  on 

Aldehydes  and  Ketones  (Grignard)  .....  67 
(b)  Action  of  Magnesium  Alkyl  or  Aryl  Halide  on  Esters,  Acyl 

Chlorides  and  Acid  Anhydrides  .  .  .  .  70 
Reaction  XV. — Action  of  Zinc  Alkyl  on  Aldehydes,  on  certain  Ketones, 

•and  on  Acyl  Chlorides        .        .        .        .        .        .  .71 

Reaction  XVI. — Action  of  certain  Oxidising  Agents  on  a-  and  (3- 

Naphthols         .........  72 


7  CHAPTER  V 

Oxy  Compounds 

Reaction    XVII. — Intramolecular    rearrangement    of     the  Glycols 

(Pinacoline  Transformation)        ......  74 

Reaction  XVIII. — Ring  Formation  by  Elimination  of  Water  from 

certain  Molecules       .        .        .        .        .        .        .  .75 

Reaction   XIX. — (a)  Condensation  of  Anthranol  Derivatives  with 

Glycerol    .        .        .        .        .  .        .  78 

(b)  Condensation  of  Anthranol  Derivatives  with  Formaldehyde  .  79 
Reaction  XX. — (a)  Action  of  Metallic  Zinc  on  a  Mixture  of  an  Aromatic 

Hydrocarbon  and  a  Derivative  of  Phthalyl  Chloride      .        .  79 

(b)  Action  of  certain  Anhydrous  Metallic  Halides  on  a  Mixture 

of  an  Aromatic  Hydrocarbon  or  certain  Derivatives  and  an 
Acyl  Halide  (Friedel-Crafts)  80 

(c)  Action  of  a  Mixture  of  Aluminium  and  Mercuric  Chloride  on  a 

Mixture  of  an  Aromatic  Hydrocarbon  and  an  Alkyl  Halide    .  84 

(d)  Combined  Action  of  Carbon  Monoxide  and  Hydrogen  Chloride 

on  an  Aromatic  Hydrocarbon  in  presence  of  a  Mixture  of 
Anhydrous  Aluminium  and  Cuprous  Chlorides  (Gattermann- 

*  Koch)       .        .        .  85 

Reaction  XXI. — (a)  Dry  Distillation  of  the  Barium  or  Calcium  Salt 

of  a  Fatty  Acid  with  Barium  or  Calcium  Formate         .        .  86 

(b)  Dry  Distillation  of  the  Barium  or  Calcium  Salts  of  Fatty  Acids  86 

(c)  Action  of  Acetic  Anhydride  on  Carboxylic  Acids  and  subsequent 

y  Distillation        .....        v        ...  87 

(d)  Catalytic  Action  of  its  Manganese  Salt  on  the  Vapour  of  a 

Fatty  Acid  88 


xii 


CONTENTS 


Reaction  XXII. — {a)  Action  of  Magnesium  Alkyl  or  Aryl  Halide  on 
(i.)  excess  of  Ethyl  Formate,  (ii.)  Ethyl  Orthoformate, 
(iii.)  di -substituted  Formamide  and  other  Derivatives  of 
Formic  Acid  (Grignard)      .......  89 

(b)  Action  of  Magnesium  Alkyl  or  Aryl  Halide  on  (i.)  Nitrites, 

fii.)  Amides  (Grignard)       .......  89 

(c)  Action  of  Zinc  Alkyl  on  Acyl  Chlorides  in  certain  proportions  .  90 
Reaction  XXIII. — (a)  Condensation  of  Ethyl  Formate  with  certain 

Oxy  Compounds  under  the  influence  of  Sodium  Ethoxide 

(Claisen)  90 

(b)  Condensation  of  Esters  other  than  Ethyl  Formate  with  certain 
Ketones  under  the  influence  of  Sodium  E  thy  late,  Metallic 
Sodium,  or  Sodamide  (Claisen)    .        .        .        .        .  .91 

Reaction  XXIV. — Condensation  of  certain  Oxy  Compounds  with  one 

another  under  the  influence  of  Dehydrating  Agents      .        .  93 

Reaction  XXV. — Action  of  an  Alkyl  Halide  on  the  Sodio -derivative  of 

certain  Ketones.        ........  94 


CHAPTER  VI 


Hydroxy-oxy  Compounds 

Reaction   XXVI. — (a)  Condensing  Action   of   Potassium  Cyanide, 
Potassium   Carbonate,    or    other   substances   on  Aliphatic 
(Claisen),  and  Aromatic  Aldehydes  (Liebig)  .        .        .  .95 
(6)  Condensing  Action  of  Potassium  Cyanide  on  a  Mixture  of  an 

Aliphatic  Aldehyde  and  a  Ketone        .....  97 

Reaction  XXVII. — Condensation  of  Chloroform  with  Phenols  and 

simultaneous  Hydrolysis  of  the  Product  (Reimer-Tiemann)    .  98 

Reaction  XXVIII. — Formation  of  an  Aldime  by  the  action  of  Hydrogen 
Chloride  and  Hydrogen  Cyanide  (HCN.HC1)  on  a  Phenol  or  a 
Phenol  Ether  in  the  presence  of  Anhydrous  Aluminium  Chloride, 
and  the  Hydrolysis  of  the  Aldime  so  formed  (Cattermann)     .  100 

Reaction    XXIX. — (a)  Condensation   of    a   Phenol   with  Phthalic 

Anhydride  to  form  a  Phthalein    .        .  .        .  .100 

(b)  Condensation  of  a  Phenol  with  Phthalic  Anhydride  to  a  deriva- 

tive of  Anthraquinone        .        .        .        .        .        .  .102 

(c)  Condensation  of  Meta-hydroxy-  and  Di-meta-dihydroxy-benzoic 

Acids  with  themselves  and  with  Benzoic  Acid  under  the 
action  of  hot  Sulphuric  Acid       .        .        .        .        .  .103 

Reaction  XXX. — Condensation  of  a  Mtrile  with  a  Phenol  or  a  Phenol 
Ether  and  Hydrolysis  of  the  resulting  Ketimine  Hydrochloride 
to  a  Ketone      .        .        .        .        .        .        .        .  .103 

Reaction  XXXI. — Action  of  Heat  on  Sodium  Formate  .  .  .105 
Reaction  XXXII. — Action  of  Alkalis  on  certain  a-di-ketones  .  .  105 
Reaction  XXXIII. — (a)  Condensation  of  an  Aromatic  Carboxylic 

Acid  with  Formaldehyde  (Lederer-Manasse)  ....  106 

(b)  Condensation  of  Malonic    Acids    with  Aldehydes  or  some 

Ketones  under  the  influence  of  Primary  and  Secondary  Amines  106 

(c)  Condensation  of  Aldehydes  with  Malonic  Acid  in  the  presence 

of  Alcoholic  Ammonia        .        .        .        .        .        .  107 

(d)  Condensation  of  Aldehydes  with  the  Sodium  Salts  of  certain 
Acids  in  the  presence  of  Acid  Anhydrides  (Perkin)        .  107 

(e)  Condensation  of  the  Dichlorides  of  Aromatic  Aldehydes  with 

the  Sodium  Salts  of  certain  Acids        .....  109 


CONTENTS 


xiii 


Reaction   XXXIV. — {a)  Condensation   of  Carbon   Dioxide  with  a 

Phenol  (Kolbe-Schmitt)      .        .        .        .        .        .  .110 

(b)  Action  of  Carbon  Dioxide  on  an  Organo -magnesium  Halide     .  112 

(c)  Action  of  Carbon  Dioxide  on  Sodium  Acetylides  in  Dry  Ether  115 
Reaction   XXXV. — (a)  Condensation  of  Phthalic  Anhydride  with 

Aromatic  Hydrocarbons  in  the  presence  of  Anhydrous  Alumi- 
nium Chloride  (Friedel-Crafts)     .        .        .        .        .  .115 

(b)  Condensation   of  Phthalic  Anhydride  with  Phenols  in  the 
presence  of  Anhydrous  Aluminium  Chloride,  s-tetrachloroethane 
being  used  as  a  Solvent      .        .        .        .        .        .  .117 

Reaction    XXXVI. — Condensation    of   Carbon    Tetrachloride  with 

Phenols  and  simultaneous  Hydrolysis  .        .        .        .  .117 

Reaction  XXXVII. — Action  of  finely  divided  Metals  on  Halogen  Acids  117 
Reaction  XXXVIII. — {a)  Action  of  Aqueous  or  Alcoholic  Potassium 
or  Sodium  Cyanide  on  Aliphatic  Halogen  Compounds  and 
Hydrolysis  of  the  Nitriles  so  formed     .        .        .        .  .118 

General  Methods  of  Isolating  Organic  Acids  from  their  Salts.        .  121 

(b)  Action  at  200°  of  Aqueous  or  Aqueous-alcoholic  Potassium 

Cyanide  in  presence  of  Cuprous  Cyanide  on  Aromatic  Halogen 
Compounds,  and  Hydrolysis  of  the  Nitriles  so  formed    .        .  121 

(c)  Action  of  Halogen  Cyanide  on  Aldehydes  and  Ketones,  and 

Hydrolysis  of  the  Cyanhydrins  so  formed  .  .  .  .121 
Reaction  XXXIX. — Fusion  of  the  Salts  of  Aromatic  Sulphonic  Acids 

with  Sodium  Formate         .        .        .        .        .        .  .124 

Reaction  XL. — Condensation  of  a  Phenol  with  a  "  Methane  Carbon 

Atom  "     .  .  124 


CHAPTER  VII 
Oxide-oxy  Compounds 

Reaction  XLI. — Elimination  of  Water  from  o-Phenoxy-benzoic  Acids  126 
Reaction  XLII. — Prolonged  action  of  Heat  on  Ethyl  Aceto-acetate    .  127 
Reaction  XLIII. — (a)  Formation  of  Esters  by  the  action  of  Acid 
Anhydrides  or  of  Acid  Chlorides  on  an  Alcohol  in  the  presence 
of  Magnesium  Alkyl  Halide  (Crignard)         .        .        .  .128 

(b)  Formation  of  Ethyl  Esters  by  the  action  of  Ethyl  Chloro- 

formate  on  Magnesium  Alkyl  Halide  in  Dry  Ethereal  Solution  128 

(c)  Condensation  of  a-Halogen  Fatty  Acid  Esters  with  Aldehydes 

and  Ketones  by  means  of  Zinc  or  Magnesium  (Reformatsky- 
Grignard)  .        .        .        .        .        .        .        .  .128 

(d)  Condensation  of  Di-ethyl  Oxalate  with  Alkyl  Halides  in  the 

presence  of  Zinc  (Frankland-Duppa)     .....  130 
Reaction  XLIV. — (a)  Condensation  of  Alkyl  and  Aryl  Halides  with 

Ethyl  Sodio-malonate  and  its  Homologues    ....  130 

(b)  Condensation  of  Alkyl  and  Aryl  Halogen  Compounds  with  the 

Sodio-  and  other  Metallo-  derivatives  of  Aceto -acetic  Ester  and 

its  Homologues  .........  132 

(c)  Condensation  of  Alkyl  and  Acyl  Halides  with  the  Sodio -deriva- 

tives of  Cyanacetic  Ester    .        .        .        .        .        .  .137 

Reaction    XLV. — Condensation   of    Aldehydes   and    Ketones  with 
certain  Esters  under  the  influence  of  Acetic  Anhydride,  Hydro- 
chloric Acid,  Sodium  Ethoxide  or  certain  Bases     .        .        .  137 
Reaction  XL VI. — Condensation  of  an  Ester  with  itself  or  with  another 

Ester  by  means  of  Sodium  Ethoxide  or  Sodamide  (Claisen)  .  140 
Reaction  XL VII. — Condensation  of  an  Ester  with  itself  by  the  action 

of  Iodine  on  its  Sodio -derivative  .        .        .        .        .  .144 


XIV 


CONTENTS 


CHAPTEE  VIII 

Nitrogen  Compounds 

page 

Keaction  XLVIII. — (a)  Action  of  Alkali  Cyanides  on  Alkyl  and  Acyl 

Halides     ..........  146 

(b)  Action  of  Alkali  Cyanides  on  Alkyl  Halogen  Sulphates  .  .147 

(c)  Action  of  di-methyl  Sulphate  on  Potassium  Cyanide  .  .  148 
Keaction   XLIX. — {a)  Action   of   Cuprous  Potassium  Cyanide  on 

Aromatic  Diazonium  Compounds  (Sandmeyer)     .        .        .  149 
(b)  Action  of  finely  divided  Copper  and  Alkali  Cyanides  on  Aromatic 

Diazonium  Compounds       .        .        .        .        .        .  .150 

Keaction  L. — (a)  Addition  of  Hydrogen  Cyanide  to  Aldehydes  or 

Ketones    ..........  150 

(b)  Condensation  of  an  Aldehyde  with  Ammonia  and  Hydrogen 

Cyanide    ...        .        .        .        .        .        .        .  152 

(e)  Action  of  Hydrogen  Cyanide  on  Quinones      .        .        .  .154 

Reaction  LI. — {a)  Action  of  Acids  on  the  non-para  substituted  Hydrazo 

compounds        .........  155 

(b)  Molecular  rearrangement  of  Di-benzanilides   .        .        .   '  .156 
Keaction  LIL — (a)  Action  of  Copper  Powder  on  2-  and  4-mono-nitro- 
and    2  :  4-di-nitro-chloro-    and    bromo -benzenes    and  their 
Homologues      .        .        .        .        .        .        .        .        .  157 

(b)  Action  of  Cuprous  Chloride  on  Nitro -diazonium  Compounds  .  157 
Reaction  LIII. — Action  of  Aceto-acetic  Ester  on  Aldehyde  Ammonias  158 
Reaction  LIV. — (a)  Condensation  of  Non-di-ortho-substituted  Primary 

Aromatic  Amines  with  Acrolein  (Skraup)      .        .        .        .  159 

(b)  Condensation  of  Primary  Aromatic  Amines  other  than  Ortho- 

substituted  with  two  Molecules  of  certain  Aldehydes  (con- 
taining the  group  — CH2CHO)  under  the  influence  of  Sulphuric 
or  Hydrochloric  Acid  .        .        .        .        .        .  .162 

(c)  Condensation    of    o-Amino-benzaldehydes   with  aldehydes, 

ketones,  aceto-acetic  ester,  etc.,  under  the  influence  of  a  trace 
of  Sodium  Hydroxide,  to  give  quinoline  derivatives       .  .163 
Reaction  LV. — Intramolecular  condensation  of  Phenyl  Hydrazones  of 
Aldehydes,  Ketones,  and  Ketonic  Acids  by  heating  with 
Hydrochloric  Chloride  or  Zinc  Chloride         .        .        .  .164 


THE  LINKING  OF  HYDROGEN  TO  GABBON 
CHAPTER  IX 
Hydrogen  Compounds 

Reaction  LVI. — Action  of  Water  on  certain  Metallic  Carbides    .  .166 
Reaction  LVII. — Action  of  Hydrogen  in  the  presence  of  finely  divided 

Nickel  on  Aromatic  Compounds  .        .        .        .        .  .167 

Reaction  LVIII. — (a)  Reduction  of  Phenols  and  Quinones  by  Distilla- 
tion with  Zinc  Dust    .        .        .        .        .        .        .  .170 

Purification  of  Crude  Anthracene       .        .        .        .        .  .171 

(b)  Reduction  of  Aromatic  Ketones  to  the  corresponding  Hydro- 
carbons by  treatment  with  Hydriodic  Acid  or  with  Sodium  in 
Alcoholic  Solution      .        .        .        .        .        .        .  .171 

Reaction  LIX. — Reduction  of  a  Primary  Aryl  Hydrazine  to  the 
corresponding  Hydrocarbon  by  the  action  of  Copper  Sulphate 
or  Ferric  Chloride      .        .        .        .        .        .        .        .  172 

Reaction  LX. — Action  of  Water  on  Magnesium  Alkyl  or  Aryl  Halides  173 
Reaction  LXI. — Reduction  of  Diazonium  Compounds  to  the  corre- 
sponding Hydrocarbon       .        .        .        .        .        .  .174 


CONTENTS 


xv 


Keaction  LXII. — Direct  reduction  of  Halogen  Compounds  .  17.-) 

Purification  by  Fractional  Liquefaction  or  Evaporation  .  176 

CHAPTER  X 
Hydroxy  Compounds  (Alcohols  and  Phenols) 

,  Reaction  LXIII. — Combined  Oxidation  and  Reduction  of  Aromatic 

Aldehydes  under  the  influence  of  Caustic  Alkalis  .        .  .178 
Reaction  LXIV. — (a)  Reduction  of  Aldehydes  and  Ketones  to  the 

corresponding  Alcohols  by  the  use  of  Alkaline  Reducing  Agents  179 

(b)  Reduction  of  Aldehydes  and  Ketones  to  the  corresponding 

Alcohols  by  the  use  of  Acid  Reducing  Agents        .        .  .180 

(c)  Reduction  of  Quinones        .        .        .        .        .  .181 

CHAPTER  XI 

oxy  and  hydpvoxy-oxy  compounds  (aldehydes,  ketones  and 

Acids) 

Reaction  LXV. — (a)  Reduction  of  Phenolic  Acids  to  the  corresponding 
Aldehydes  by  the  action  of  Sodium  Amalgam  and  Boric  Acid 
in  the  presence  of  a  Primary  Aromatic  Amine       .        .  .183 
(b)  Reduction  of  Lactones  to  the  corresponding  Hydroxy  Aldehydes 

by  the  action  of  Sodium  Amalgam  in  faintly  Acid  Solution    .  184 
Reaction  LXVI. — {a)  Reduction  of  Unsaturated  Acids  by  means  of 

Sodium  Amalgam  in  Alkaline  Solution         .        .        .  .185 

(b)  Reduction  of  Hydroxy  Acids  by  the  action  of  Hydriodic  Acid.  186 
Reaction  LXVII. — (a)  Ketonic  Hydrolysis  of  Alkyl  Derivatives  of 

Aceto-acetic  Ester      .        .        .        .        .        .        .  .187 

(b)  Acid  Hydrolysis  of  Alkyl  Derivatives  of  Aceto-acetic  Ester    .  188 

,  CHAPTER  XII 

Halogen  Compounds 

Reaction  LXVIII. — Simultaneous  reduction  and  Halogenation  of 

Polyhydric  Alcohols  .        .        .        .        .        .        .        .  190 

Reaction  LXIX. — Partial  reduction  of  Tri-halogen  to  Di-halogen 


Compounds       .        .        .        .  .        .        .        .  19^ 

THE  LINKING  OF  OXYGEN  TO  CARBON 

CHAPTER  XIII 
Hydroxy  Compounds  (Alcohols  and  Phenols) 

Reaction  LXX. — Oxidation  of  certain  Hydrocarbons  .  .  .193 
Reaction  LXXI. — Replacement  of  Halogen  by  Hydroxyl  .        .  .194 


Reaction  LXXII. — Replacement  of  the  Diazo  Group  by  Hydroxyl  .  198 
Reaction  LXXIII. — Direct  replacement  of  the  Aromatic  Ammo-group 

by  Hydroxyl   201 

Reaction  LXXIV. — Action  of  Mineral  Acids  on  Phenyl-hydroxylamine  203 
Reaction  LXXV. — Fusion  of  Aromatic  Sulphonic  Acids  with  Caustic 

Alkalis   213 

Reaction  LXXVI. — Addition  of  Hydroxyl  to  Ethvlenic  Bonds.        .  205 

Purification  of  Methyl  Alcohol   206 

Purification  of  Ethyl  Alcohol   207 


xvi 


CONTENTS 


CHAPTER  XIV  1 
Oxide  Compounds  (Ethers) 

page  ( 

Reaction  LXXVIL— Action  of  Sulphuric  Acid  on  an  Alcohol  or  a 

Mixture  of  Alcohols    ........  208 

Purification  of  Commercial  Ether       ......     209  • 

Reaction  LXXVIII. — Action  of  Alkyl  Halides  on  Alkali  Alcoholates 

or  Phenates       .        .        .        .        .        .        ...  -      .        .  209 

Reaction  LXXIX. — Action  of  Dimethyl  Sulphate  on  Hydroxy  Com- 
pounds    .        .        .        .        .        .        .        .        .  .211 

Reaction  LXXX. — Action  of  very  Dilute  Methyl  Alcoholic  Hydrogen 

Chloride  on  the  Sugars       .        .        .        .        .        .  214  ' 

Reaction  LXXXI. — Action  of  Hydrogen  Chloride  on  a  Mixture  of  an 

Aldehyde  and  an  Alcohol    .        .        .        .        .        .  .215, 

Reaction  LXXX II. — Condensation  of  an  Aldehyde  with  itself  under 

the  action  of  Mineral  Acids  or  of  Calcium  Chloride        .        .  215 

Reaction  LXXX  III. — Action  of  Caustic  Alkali  on  a,  /3-chlorhydrins  .    216  a 

Reaction  LXXXI V. — Addition  of  Phenols  to  Quinones     .        .  .217 


CHAPTER  XV 

Oxy  Compounds  (Aldehydes,  Ketones  and  Quinones)  « 

Reaction   LXXXV. — Simultaneous    Oxidation    and    Hydrolysis  of 

Mono -halogen  Compounds  ....        .        .  219  ^, 

Reaction  LXXX VI. — Hydrolysis  of  certain  Di-halogen  Compounds    .  219 
Reaction  LXXX VI I. — Hydrolysis  of  certain  Anils    ....  220 

Reaction  LXXX  VIII. — Action  of  Nitrous  Acid  on  the  Monoximes  of  ^ 
o-Di-ketones      .        .        .        .        .        .        .        .  .221 

Reaction  LXXXIX. — Hydrolysis  of  Nitriles  to  Amides     .        .        .  222 
Reaction  XC. — Hydrolysis  of  the  Di-saccharoses      ....  223 

Reaction  XCI. — (a)  Oxidation  of  Aromatic  Hydrocarbons  to  Aldehydes 
by  the  action  of  Chromyl  Chloride  in  Carbon  Disulphide 
Solution  (Etard)   224  f 

(b)  Oxidation  of  Aromatic  Hydrocarbons  to  Aldehydes  by  the 

action  of  Chromic  Acid  in  Acetic  Anhydride  Solution    .        .  225 

(c)  Oxidation  of  Aromatic  Hydrocarbons  to  Aldehydes  by  the 
action  of  Cerium  Dioxide  in  presence  of  Concentrated  Sulphuric 


Acid   225 

Reaction  XCII. — Action  of  Oxidising  Agents  on  Methylene  Groups  in 

Aromatic  Compounds         .......  226 

Reaction  XCIII. — Oxidation  of  Aromatic  Hydrocarbons  to  Quinones  .  227 
Reaction  XCIV. — Oxidation  of  Primary  Aromatic  Amines  and  their 

;para-substituted  Derivatives  to  Quinones    .....  228 


CHAPTER  XVI 
Hydeoxy-oxy  Compounds  (Acids) 

Reaction  XCV.— Hydrolysis  of  Nitriles  232 

Reaction  XCVI. — Hydrolysis  of  Esters  to  Acids  ....  234 
Reaction  XCVII. — Hydrolysis  of  Amides,  Acyl  Chlorides  and  Acid 

Anhydrides  236 

Reaction    XCVIIL — Simultaneous    Oxidation    and    Hydrolysis  of 

Benzyl  and  Benzal  Chlorides  and  their  Derivatives  .  .  236 
Reaction  XCIX. — Oxidation  of  certain  Carbon  Compounds  to  less 

Complex  Compounds  ........  237 


CONTENTS 


xvii 


PAGE 

Eeaction  C. — Oxidation  of  the  Side  Chain  in  Aromatic  Compounds    .  237 
Reaction  CI. — (a)  Oxidation  of  Primary  Alcohols  to  the  corresponding 

Carhoxylic  Acids        .        .        .        .        .        .        .  .241 

(b)  Oxidation  of  Aldehydes  to  Carboxylic  Acids  .        .  .  242 


CHAPTER  XVII 
Oxide-oxy  Compounds  (Esters  and  Acid  Anhydrides) 


Reaction  CII. — Direct  Action  of  an  Acid  on  an  Alcohol     .        .        .  246 

Reaction  CIII. — Continual  removal  of  Water  in  a  suitable  Apparatus.  248 
Reaction  CIV. — Use  of  Concentrated  Sulphuric  Acid  or  of  Hydrogen 

Chloride  to  promote  Esterification        .        .        .        .        .  249 

Reaction  CV. — Action  of  Acid  Anhydrides  on  Alcohols  and  Phenols    .  251 

Reaction  CVI. — Action  of  Acyl  Chlorides  on  Alcohols  .  .  .  253 
Reaction  CVII. — Action  of  an  Alkyl  Iodide  on  the  Silver  Salt  of  an 

Acid   .  .256 

Reaction  CVIII. — Polymerisation  of  an  Aldehyde  to  an  Ester    .        .  257 

Reaction  CIX. — Action  of  Heat  on  certain  Dibasic  Acids  .  .  .  257 
Reaction  CX. — Action  of  an  Acyl  Chloride  on  the  Sodium  Salt  of  an 

Acid   258 

Reaction  CXI. — Action  of  Dehydrating  Agents  on  a  Free  Acid  .        .  259 

Reaction  CXII. — Action  of  certain  Bases  on  Acyl  Chlorides       .        .  260 


THE  LINKING  OF  NITROGEN  TO  CAEBON 
CHAPTER  XVIII 
Nitro  Compounds 

Reaction  CXIII. — Action  of  Dilute  Nitric  Acid  on  some  Organic 

Compounds       .        .        .        .        .        .        .        .  .261 

Reaction  CXIV. — Action  of  Concentrated  Nitric  Acid  on  Aromatic 

Compounds       .        .        .        .        .        .        .        .  .261 

Reaction  CXV. — Action  of  a  Mixture  of  Concentrated  Nitric  and 
Concentrated  Sulphuric  Acids  (mixed  acid)  on  Aromatic 
Compounds       .........  262 

Rules  of  Nitration  263 

Analysis  of  a  Mixed  Acid  ........  263 

The  Isolation  of  Nitro  Compounds      ......  264 

Reaction  CXVI. — Action  of  Nascent  Nitric  Acid  on  Aromatic  Com- 
pounds in  presence  of  Concentrated  Sulphuric  Acid      .        .  269 

Reaction  CXVII. — Action  of  Nitrous  Fumes  on  certain  Organic  Com- 
pounds     .        .        .        .        .        .        .        •        .  .271 

Reaction  CXVIII. — Action  of  Nitrous  Acid  on  Aromatic  Amines  in 

presence  of  Cuprous  Salts  (Sandmeyer)         .        .        .  .273 

Reaction  CXIX. — Action  of  Silver  Nitrite  on  Alkyl  Halides       .        .  273 

Reaction  CXX. — Action  of  Concentrated  Nitric  Acid  on  certain 

Sulphonic  Acids  274 

.   Reaction  CXXI. — Action  of  Tetranitromethane  on  Bases  .        .        .  274 

CHAPTER  XIX 

Reaction  CXXII. — Action  of  Phenols  and  Primary  Aromatic  Amines 

on  Diazonium  Compounds  .......  275 

Reaction  CXXIII. — Action  of  Nitrous  Acids  on  Phenols,  and  Tertiary 

Aromatic  Amines       .        .        .        .        .        .        .  .276 

s.o.c.  b 


xviii 


CONTENTS 


PAGE  I 

Reaction  CXXIV. — Action  of  Nitrous  Acid  on  Secondary  Amines,  and 


subsequent  Eearrangement  of  the  Products.        .        .        .  278 
Eeaction  CXXV.— Action  of  Alkyl  Halides  on  Phthalimide  (Potassium 

Salt)  279 

Eeaction  CXXVI. — Action  of   Hydroxylamine  on  Aldehydes  and 

Ketones   279  ' 

Eeaction  CXXVII. — Action  of  Acids.  Acid  Chlorides,  Anhydrides  and 

Phosphorus  Pentachloride  on  Oximes  (Beckmann)         .  .281 
Eeaction  CXXVIII. — Action  of  Phenylhydrazine,  etc.,  on  Aldehydes 

and  Ketones      .........  282 

Eeaction   CXXIX. — Action   of   Semicarbazide   on   Aldehydes  and 

Ketones   284  * 

Eeaction  CXXX. — Formation  of  Amino  Gruanidine  Derivatives         .  285 
Eeaction  CXXXI. — Formation  of  Semioxamazones  ....    285  c 
Eeaction  CXXXII. — Action  of  Aliphatic  Halogen  Compounds  on 

Aliphatic  or  Aromatic  Primary  Amines        .        .        .  .286 
Eeaction  CXXXIII. — Action  of  Aromatic  Halogen  Compounds  on  t 

Ammonia  or  Amino  Compounds  .        .        .        .        .  .289 

Eeaction  CXXXIV.— Action  of  Silver  Cyanide  on  Alkyl  Halides        .  290 
Eeaction  CXXXV. — Action  of  Chloroform  and  Alcoholic  Potash  on 

Aliphatic  and  Aromatic  Primary  Amines      ....  290 
Eeaction  CXXXVI. — Action  of  the  Hydrochloride  of  a  Primary 

Aromatic  Base  on  the  Base         ......    290  1 

Eeaction  CXXXVII. — Action  of  Bromine  (or  Chlorine)  and  Alkali  on 

certain  Amides  and  Imides  (Hofmann) .        .        .        .  291  i 

Eeaction  CXXXVIIL— Action  of  Heat  of  Ammonium  Salts      .        .  292 


Eeaction  CXXXIX. — Action  of  Ammonia  on  Esters,  Acid  Chlorides 

or  Anhydrides   .        .        .        .        .        .        .        .        .  293 

Eeaction  CXL. — Action  of  Ammonia  on  Phenols  and  Sulphonic  Acids  294 
Eeaction  CXLI. — Action  of  Acids,  Acid  Anhydrides  and  Chlorides  on 

Primary  and  Secondary  Amines  ......  296  i 

Eeaction  CXLII. — Action  of  Primary  Aromatic  Amines  on  Alcohols  .  298 
Eeaction  CXLIII. — Condensation  of  Aromatic  Aldehydes  with  Primary 

Aromatic  Amines       ........  299  j 

Eeaction  CXLIV. — Action  of  Ammonia  on  Aldehydes       .        .        .  300 

Eeaction  CXLV. — Action  of  Nitrous  Acid  on  certain  Ketones    .  t      .  301 


THE  LINKING  OF  SULPHUR  TO  CARBON 
CHAPTEE  XX 
Sulphonic  Acids 
Eeaction  CXLVI. — Action  of  Concentrated  Sulphuric  Acid  on  Hydro- 


carbons or  Substituted  Hydrocarbons  .....  302 

Isolation  of  Sulphonic  Acids      .        .  .        .        .        .  302 

Tests  for  Complete  Sulphonation        .        .  .        .  .303 

Apparatus  Used  in  Sulphonation        .        .        .        .        .        .  303 

Eeaction  CXLVII. — Action  of  Fuming  Sulphuric  Acid  (oleum)  on 

Hydrocarbons  or  Substituted  Hydrocarbons  .        .        .  305 

Estimation  of  S03  in  Oleum      .        .        .        .        .        .  .305 

Preparation  of  Oleum  of  a  given  Strength  .....  306 

Eeaction  CXLVII  I. — Action  of  Chloro -sulphonic  Acid  on  Hydro - 

*•  carbons  or  Substituted  Hydrocarbons  .        .        .        .  309 

Eeaction  CXLIX. — Intramolecular  Eearrangement  of  Aromatic  Amine 

Sulphates.        .        .        .        .        .        .        .        .  .311 


CONTENTS 


xix 


PAGE 

Reaction  CL. — Action  of  Sulphites  and  Bisulphites  on  Substituted 

Hydrocarbons    .        .        .        .        .        .        .        .  .312 

(a)  Replacement  of  Halogen      .        .        .        .        .        .  312 

(b)  Simultaneous  Reduction  and  Sulphonation     .        .        .  .312 

(c)  Alkyl  Sulphonic  Acids  .  312 

(d)  Olefinic  Compounds     .        .      ■  .        .        .        .        .  .312 

Reaction  CLI. — Action  of  Poly-sulphates  on  certain  Hydrocarbons     .  316 

Reactions  of  the  Sulphonic  Croup      .        .        .        .        .  •  316 


CHAPTER  XXI 

Reaction  CLII. — Action  of  Sulphur  and  Sodium  Sulphide  on  Aromatic 

Bases       .        .        .        .        .        .        .        .        .       \  317 

Reaction  CLIII. — Action  of  Sulphur  Dioxide  on  Aromatic  Hydro- 
carbons in  presence  of  Aluminium  Chloride  or  Mercuric 
Chloride  318 

Reaction  CLIV. — Action  of  Sulphur  Dioxide  on  a  Diazonium  Com- 
pound in  presence  of  finely  divided  Copper   .        .        .  .319 

Reaction  CLV. — Action  of  Potassium  Xanthate  on  Diazonium  Com- 
pounds with  Subsequent  Hydrolysis  and  Oxidation      .        .  320 

Reaction  CLVI. — Action  of  Hydrogen  Sulphide  on  Diazonium  Com- 
pounds    .        .        .        .        .        .        .        .        .        .  320 

Reaction  CLVII. — Action  of  Hydrosulphides  on  Alkyl  Halides  or 

Sulphates,  or  on  certain  Aromatic  Halogen  Derivatives         .  321 

Reaction  CLVIII. — Action  of  Phosphorus  Pentasulphide  on  Acids  or 

Alcohols  322 

Reaction  CLIX. — Action  of  Sulphonyl  Chlorides  on  Hydrocarbons  in 

presence  of  Aluminium  Chloride  .        .        .        .        .  .322 

Reaction  CLX. — Action  of  Phosphorus  Pentasulphide  on  Ethers        .  322 

Reaction  CLXI. — Action  of  Sodium  or  Potassium  Sulphide  on  Alkyl 

Halides  or  Alkyl  Sulphates  .        .  ■  .        .        .        .  322 


THE  LINKING  OF  HALOGEN  TO  CARBON 
CHAPTER  XXII 

Reaction  CLXII. — Replacement  of  Oxygen  and  Hydroxyl  by  Halogens  323 
Reaction  CLXIII. — Addition  of  Halogen  or  Halogen  Hydride  to 

Unsaturated  Compounds     .        .        .        .        .        .  .331 

Reaction  CLXIV. — Replacement  of  Hydrogen  by  Nascent  Halogen  .  335 
Reaction  CLXV. — Replacement  of  Hydrogen  by  Use  of  Halogen 

Compounds       .........  336 

Reaction  CLXVL — Replacement  of  the  Amino  Croup  by  Halogen  .  338 
Reaction  CLXVII. — Replacement  of  Halogen  by  Halogen.  .  .  340 
Reaction  CLXVIII. — Replacement  of  Hydrogen  by  Molecular  Halogen  341 


THE  LINKING  OF  HYDROGEN  TO  NITROGEN 
CHAPTER  XXIII 

Amino  Compounds 

Reaction  CLXIX. — Action  of  Metals  on  Nitro  Compounds  in  Acid 

Solution  350 

Reaction  CLXX. — Action  of  Metals  on  Nitro  Compounds  in  Alkaline 

Solution    ..........  355 


XX 


CONTENTS 


PAGE 

Reaction  CLXXI. — Action  of  Alkali  Sulphides  and  Hydrosulphides 

on  Nitro  Compounds  .        .        .  .        .        .        .  357 

Reaction  CLXXII. — Action  of  Reducing  Agents  on  Azo  Compounds.  359 

Reaction  CLXXIII. — Action  of  Reducing  Agents  on  Nitroso  Com- 
pounds    .        .        .        .        .        .        .        .        .  360 

Reaction  CLXXIV. — Reduction  of  Oximes  to  Amines  with  Metallic 

Sodium  or  Sodium  Amalgam       .        .        .        .        .  .360 

CHAPTER  XXIV 

Reaction  CLXXV. — Action  of  Metallic  Zinc  on  Nitro  Compounds  in 

Neutral  Solution  363 

Reaction  CLXXVI. — Action  of  Reducing  Agents  on  Diazonium  Com- 
pounds    ..........  363 


THE  LINKING  OF  NITROGEN  TO  NITROGEN 

CHAPTER  XXV 
Reaction  CLXXVII. — Action  of  Nitrous  Acid  on  Primary  Aromatic 


Amines     ..........  365 

Preparation  of  Diazonium  Compounds        .        .        .        .  .366 

Reactions  of  Diazonium  Compounds  .        .        .        .        .  .369 

Reaction    CLXXVIII. — Action   of   Alkaline    Reducing   Agents  on 

Aromatic  Nitro  Compounds         .        .        .        .        .  .371 

CHAPTER  XXVI 
Dyes 

Azo  Dyes   372 

Di-  and  Tri-Aryl  Methane  Dyes        .        .        .       •.'  .  374 

Pyrone  or  Phthalein  Dyes        .......  378 

Nitro  Dyes  .       .       .        .    .   .        ..."   379. 

Thiazine  Dyes     ..........  380 

Indigoid  Dyes      .        .        .        .        .        .        .        .        .        .  382 

Anthraquinone  Dyes  ...        .        .        .        .        .        .  384 

CHAPTER  XXVII 
Drugs  386 

CHAPTER  XXVIII 
Electrolytic  Preparations         .        .        .        .        .        •  .391 

CHAPTER  XXIX 
Products  from  Natural  Sources        ......  394 

CHAPTER  XXX 

Stereochemical  Reactions  ........  399 


CHAPTER  XXXI 
Decompositions    .        .        .       .       .       .       .  •       •  403 


CONTENTS 

CHAPTER  XXXII 
Miscellaneous  Preparations 

PART  III 
CHAPTER  XXXIII 


Detection  of  Elements  present  in  Carbon  Compounds      .        .  435 

CHAPTER  XXXIV 

Quantitative  Estimation  of  Carbon  and  Hydrogen   .        .        .  438 

Modifications  of  the  Method  and  other  Notes       ....  446 

Combustion  of  Substances  containing  Nitrogen    ....  448 

Combustion  of  Substances  containing  Sulphur  or  Halogen   .        .  449 

Combustion  of  Substances  containing  Metallic  Radicles        .        .  449 


CHAPTER  XXXV 

Quantitative  Estimation  of  Nitrogen        .        .        .        .        .  450 
Dumas  Method — 

(a)  Closed  Tube         .        r  .        .        .  .  .450 

(b)  Open  Tube  .        .        .        .     .  454 

Further  Notes   .........  455 

Kjeldahl  Method   .        .  .456 

CHAPTER  XXXVI 

Quantitative  Estimation  of  Halogens  and  Sulphur  .        .        .  458 

Carius  Method  (for  halogens)      .....                 .  458 

Pira  and  Schiff  Method  (for  halogens)   460 

Robertson  Method  (for  halogens)        ....        .  .461 

Carius  Method  (for  sulphur)       .......  463 

Fusion  Method  (for  sulphur)      .......  463 

Simultaneous  Determination  of  Halogens  and  Sulphur.        .        .  464 


xxi 

PAG  E 

415 


*  CHAPTER  XXXVII 

Molecular  Weight  Determination      ......  465 

Victor  Meyer  Method  •  .465 

Freezing  Point  Method  466 

Boiling  Point  Method        .        ...        .        .        .        .  469 


CHAPTER  XXXVIII 

Determination  of  the  Equivalent  of  an  Acid  ...  .  .  472 
Determination  of  the  Equivalent  of  a  Base     ....  474 


xxii 


CONTENTS 


CHAPTER  XXXIX 


Group  Estimations 

PAGE 

Estimation  of  Primary  or  Secondary  Amines  by  Acetylation    .  475 

Estimation  of  the  Number  of  Hydroxyl  Groups  in  a  Compound  .  475 

Estimation  of  Acyl  Derivatives         ......  476 

Estimation  of  Methoxyl  or  Ethoxyl  Groups     ....  476 

Estimation  of  Esters  .........  479 

Estimation  of  Amides  .        .        .        .        .        .        . 1              .  479 

Estimation  of  Aldehydes  (other  than  Formaldehyde)        .        .  479 

Estimation  of  Formaldehyde      .               .        .        .        .        .  480 

CHAPTER  XL 

Estimations  based  on  the  Use  of  Titanous  Chloride  .        . '       .  482 

Estimation  of  Nitro  Compounds         ......  483 

Estimation  of  Nitroso  Compounds      .....        .  484 

Estimation  of  Dyes  .........  485 

CHAPTER  XLI 

Estimations  based  on  Diazotisation  or  Coupling       .        .  .487 
Preparation  of  Standard  Reagents      .        .        .        .        .  .487 

Estimation  of  Amines       .        .        .        .        .        .        .  .489 

Estimation  of  Phenolic  Compounds    .        .        .        .                .  490 

Estimation  of  H  Acid        .                .        .        .        ...        .  490 

CHAPTER  XL  1 1 

Miscellaneous  Estimations  ........  492 

Estimation  of  j9-Phenylenediamine     .        .        .                •        •  492 

Estimation  of  Thioph en  in  Benzene    .        ...        .        .        .  493 

Estimation  of  Enol  Modification        .        .        .        .        .        .  493 

Estimation  of  Anthracene         .......  494 

Estimation  of  Acetone      .        .        .        .        .        .        .  494  , 

Estimation  of  Glucose  or  Cane  Sugar  .        .        .        .        .        .  496 


PART  IV 
CHAPTER  XLIII 

Inorganic  Section       .........  498 

Reagents         .        .        .        .        .        .        ...        .  498  4 

Test  Papers  and  Solutions         .......  500 

Preparations    ....        .        .        .        .        .        .  502 

Tables    .        .        .   509 


CHAPTER  XLIV 

Tests  for  the  Common  Organic  Acids        .  .  .  .  .512 

Tests  for  Alkaloids    .        .        .        .        .  .  .  .  .519 

Tests  for  Carbohydrates    .        .        .        .  .  .  .  .  523 


Index 


525 


SYSTEMATIC  ORGANIC  CHEMISTRY 


PART  1 


CHAPTER  I 


INTRODUCTORY 


Cautions. 


1.  Fire. — (a)  Fire  extinguishers  should  always  be  at  hand  in  the 
laboratory,  and  should  be  applied  at  once. 

(b)  Great  care  is  necessary  in  the  use  of  ether,  light  petroleum,  carbon 
disulphide,  acetone,  alcohol,  benzene,  etc.,  as  the  vapours  of  these  are 
highly  inflammable.  They  should  always  be  distilled  from  a  water  bath 
and  be  collected  in  the  apparatus  shown  on  p.  18.  Special  care  is 
necessary  with  carbon  disulphide,  as  its  vapour  inflames  in  contact  with 
a  warm  surface,  even  in  the  absence  of  a  flame. 

(c)  If  the  liquid  in  a  beaker  or  flask  catches  fire,  the  source  of  heat 
should  be  removed,  and  the  flame  extinguished  by  placing  a  watchglass 
on  the  opening  of  the  vessel. 

(d)  A  blanket  should  be  at  hand  in  case  the  clothes  catch  fire. 

2.  Poison. — (a)  All  operations  in  which  fumes  or  noxious  vapours  are 
evolved  must  be  carried  out  in  a  good  fume  cupboard. 

(b)  Special  care  must  be  taken  not  to  breathe  vapours  of  the  following  : 
strong  or  fuming  acids,  cyanogen,  hydrogen  cyanide,  carbon  monoxide, 
halogens,  phosgene,  alkyl  sulphates,  acyl  chlorides,  nitro  compounds,  etc. 

(c)  The  hands  should  be  immediately  washed  after  using  poisonous 
substances  such  as  alkaloids,  potassium  or  sodium  cyanide,  arsenious 
oxide,  phosphorus.  This  precaution  could  be  extended  to  the  majority 
of  organic  compounds. 

3.  Accidents. — (a)  A  First- Aid  outfit  should  be  kept  in  each  laboratory. 


j  (6)  For  burns  by  heat,  cover  with  carron  oil  or  paint  with  solution  of 
picric  acid.    Carron  oil  =  linseed  oil  +  lime  water  (equal  parts). 

(c)  For  acid  burns  (1)  on  the  skin  ;  wash  with  much  water  and  with 
dilute  ammonia,  or  bicarbonate  solution  ;  apply  carron  oil  when  dry. 
(2)  in  the  eye  ;  use  much  saturated  solution  of  borax. 

(d)  For  alkalis  (1)  on  the  skin  ;  wash  with  much  water,  then  with  1% 
acetic  acid.  (2)  in  the  eye  ;  use  much  saturated  boric  acid  solution  and 
then  drop  in  castor  oil. 

(e)  For  acid  on  the  clothes  wash  with  ammonium  carbonate  solution. 
(/)  For  alkali  on  the  clothes,  wash  with  dilute  acetic  or  boric  acids,  and 

remove  remaining  acid  with  ammonium  carbonate  solution. 

(g)  For  bromine  on  the  skin,  wash  with  alcohol,  then  with  carron  oil. 

S.O.C.  1  B 


2 


SYSTEMATIC  ORGANIC  CHEMISTRY 


All  these  remedies  should  be  kept  on  a  special  shelf  in  the  laboratory. 

Sodium  Residues. — These  should  not  be  dropped  into  the  sink  or  waste 
box,  but  should  be  added  in  small  portions  to  alcohol,  and  when  all  action 
has  ceased,  the  solution  poured  into  the  sink. 

Scheme  of  Arrangement  of  Reactions. 

The  reactions  in  this  book  are  grouped  in  sections  determined  by  the 
linking  of  elements  that  occurs  in  the  reaction  to  form  the  product.  The 
order  of  the  sections  depends  on  the  Richter  alphabet— C,  H,  0,  N,  CI,  Br, 
I,  S,  etc.  A  complete  classification  by  this  method  would  take  the 
following  form  ; — 


I.    Reactions  in  which  C, 
H, 
0, 
N, 
CI,  Br,  I, 
S,  etc., 

II.    Reactions  in  which  H, 

0, 

N, 

CI,  Br,  I, 
S,  etc., 

III.    Reactions  in  which  H, 

0, 
N, 

CI,  Br,  I, 
S,  etc.,  j 


>  are  linked  to  C. 


are  linked  to  0. 


are  linked  to  N. 


and  so  on. 

Small  sections  as  III.  are  not  further  subdivided  in  practice.  Large 
sections  are  subdivided  to  give  a  separate  subsection  for  the  linking  of 
each  separate  element  to  the  main  one,  so  to  speak,  of  the  section ;  and  each 
subsection  is  further  subdivided  according  to  the  type  of  compounds 
necessarily  obtained  in  the  various  reactions.  An  examination  of  the 
table  of  contents  and  of  the  C  to  C  section  will  make  all  the  details  clear. 
In  the  various  sections  the  reactions  follow  one  another  so  that  related 
reactions  come  together  as  much  as  possible. 

Of  course  in  practice  points  arise  which  have  to  be  settled  arbitrarily. 
Some  reactions  can  be  placed  under  two  or  more  headings,  e.g.,  C6H5SH 
— >  C6H5S03H  might  be  put  under  S  to  0  or  0  to  S.  In  this  case  it  is 
more  natural  to  put  it  in  the  latter  section,  but  in  analogous  cases  the 
doubtful  reaction  is  classified  under  the  section  first  occurring.  No 
linkings  to  H  are  considered,  H  is  always  supposed  to  be  linked  to  the 
other  element.  Some  sections  do  not  appear  in  the  book  because  so  few 
reactions  fall  within  them. 

Decomposition  reactions  in  which  links  are  broken  rather  than  made, 
electrolytic  preparations  and  some  others  are  placed  in  a  separate  section. 


INTRODUCTORY 


3 


The  name  in  brackets  above  some  preparations  is  the  structural  name  as 
far  as  one  exists.  In  the  many  cases  where  no  definite  structural  name 
exists,  an  alternative  name,  simply,  is  given. 

Hints  to  Students. 

1.  Before  commencing  a  course  on  practical  organic  chemistry,  become 
familiar  with  the  chapter  on  apparatus  and  methods.  This  chapter  must 
be  continually  referred  to  as  the  course  proceeds,  so  that  facility  in 
manipulative  detail  may  be  gained. 

2.  Before  beginning  any  individual  preparation  read  carefully  the 
entire  method  and  also  obtain  a  clear  idea  of  the  theory  as  well  as  the 
practice  of  the  operation.    Know  the  reason  for  every  step  in  the  process. 

3.  Work  on  a  definite  plan,  never  omitting  anything  essential  for  the 
sake  of  speed. 

4.  Procure  suitable  and  sufficient  apparatus.  This  applies  especially  to 
the  use  of  vessels  appropriate  to  the  quantities  to  be  used. 

5.  Clean,  and  if  necessary,  dry  all  apparatus  before  use. 

6.  Fit  up  the  apparatus  carefully  and  compactly,  paying  particular 
attention  to  the  boring  and  fitting  of  corks. 

7.  Follow  exactly  the  instructions  given.  Definite  times,  temperatures 
and  weights  are  not  specified  for  nothing. 

8.  Cultivate  a  habit  of  observation  ;  observe  all  changes  and  record 
them.    This  is  one  of  the  essentials  of  successful  research. 

9.  Whenever  possible  control  the  course  of  the  reaction  by  testing 
samples.  This  will  in  many  cases  enable  the  end  point  to  be  determined 
exactly  (see  Acetanilide,  Benzenesulphonic  Acid). 

10.  Remember  that  the  criterion  of  practical  work  is  the  yield  of  pure 
substance  obtained,  and  if  this  differs  by  more  than  10%  from  the  yield 
stated,  seek  the  cause  of  this  difference,  and  then  repeat  the  experiment. 

11.  After  the  experiment  expand  the  notes  already  taken,  giving  par- 
ticulars of  the  yield,  physical  characteristics  (M.P.,  B.P.,  D.}  and  micro- 
scopic examination  for  crystalline  form)  of  the  product.  The  ratio  of  the 
yield  obtained  to  the  theoretical  yield  also  should  be  recorded  as  a  per- 
centage. 

12.  Cost  the  preparation  (see  p.  5)  and  compare  the  price  with  the 
current  value  if  quoted. 

13.  A  sample  of  each  stable  product  should  be  kept  in  a  specimen  bottle, 
and  details  of  physical  characteristics  and  the  yield  placed  on  the  label. 

14.  Above  all,  keep  the  bench  neat  and  clean.  Use  separate  dusters 
for  it  and  for  the  apparatus. 

The  Use  of  the  Library. 

The  references  given  in  this  book  to  the  reactions  and  preparations 
should  be.  consulted  where  possible  by  the  student. 

A  knowledge  of  the  literature  is  of  fundamental  importance.  Richter's 
Lexicon  must  be  used  where  a  reference  for  a  preparation  is  not  available, 
the  method  of  using  which  is  given  fully  in  the  preface  to  that  book.  To 

b  2 


4 


SYSTEMATIC  ORGANIC  CHEMISTRY 


facilitate  the  use  of  this  lexicon,  molecular  formula)  have  been  given  in 
this  book. 

Richter  also  gives  references  to  Beilstein  which  should  afterwards  be 
consulted,  and  the  latter  book  always  gives  an  indication  of  the  scope  of 
the  reference. 

Cultivate  a  habit  of  reading  the  current  journals,  especially  J.  C.  S., 
J.  S.  C.  I.,  Berichte  and  Am.  Soc.  Do  not  forget  that  organic  chemistry  is 
not  the  only  branch  of  the  subject. 

Suggested  Lists  of  Preparations. 

Before  commencing  a  course  in  practical  organic  chemistry,  the  student 
should  have  a  definite  list  of  preparations  to  follow.  These  should  be 
arranged  in  increasing  order  of  difficulty,  and  in  such  a  way  that,  as  far 
as  possible,  each  preparation  leads  naturally  to  the  next.  Where  several 
students  are  working  in  the  laboratory,  the  best  results  are  obtained 
when  each  works  through  a  different  list  and  compares  notes  with  his 
neighbour. 

The  following  lists  are  suggested  : — 


I. 

II. 

III. 

IV. 

1 

X 

No 

196 

No. 

141 

No.  320 

No.  478 

2 

55 

263,  266 

5  5 

320 

,5  181 

5,  310 

3 

55 

33,  35 

5  5 

215 

„  192 

5,  215 

"i 

55 

408,  479 

55 

195,  197 

55  158 

55  440 

5 

55 

73 

55 

99 

„  482 

55  223 

6 

55 

181 

55 

374 

„  337 

„  359 

,7 

*> 

246 

55 

425 

,5  271 

5,  384 

8 

)i 

225 

55 

221 

5,  227 

55  184 

9 

9i 

360 

5  5 

358 

5,  286 

5,  214 

10 

5  5 

291 

55 

290 

„  363 

„  268 

]1 

55 

383 

5J 

385 

5,  275 

„  '  186,  262 

12 

5* 

222 

5  5 

282 

„  240 

„  486 

INTRODUCTORY 


5 


I.  IT.  III.  IV. 


13 

No. 

370 

No. 

138 

No.  290 

No. 

375 

14 

368 

55 

238 

,5  382 

5  1 

457 

15 

5  5 

129 

11 

338 

„  106 

1 1 

287 

16 

1  1 

242 

1  1 

28,  34 

„  44 

55 

397 

17 

55 

245 

292 

„    24,  164 

11 

136 

18 

1 1 

342 

1  1 

345 

,5  204 

1 1 

269 

19 

1 1 

390 

11 

275 

„  344 

55 

41 

20 

55 

389 

55 

20,  55 

55  155 

55 

441 

21 

1 1 

19,  54 

5  5 

392 

„  20 

5  5 

49,  50 

More  advanced  students  should  work  through  a  synthesis  involving 
several  steps,  e.g.,  Collidine,  and  should  also  attempt  the  preparation  of 
homologues  of  some  of  the  substances  given  in  detail.  In  the  lists  given 
above,  several  preparations  of  industrial  importance  are  included. 

Note  on  Costing. 

The  student  should  always  acquaint  himself  with  the  cost  of  the  materials 
he  uses  in  a  preparation.  He  should  therefore  consult  the  price-list  of 
some  well-known  manufacturer  or  retailer.  In  fact,  a  copy  of  such  a 
price-list  should  be  on  the  wall  of  every  laboratory.  Having  ascertained 
such  prices,  he  should  also,  after  finishing  his  preparation,  ascertain  the 
price  of  his  final  product  from  the  price-list  to  see  if  he  is  making  the  pro- 
duct economically.  Of  course,  many  other  factors  influence  the  market 
prices,  such  as  labour,  recovery  of  by-products,  etc.,  and  so  on,  but  it  is 
a  good  exercise  to  see  in  how  far  his  estimated  price  agrees  with  the  price- 
list.  For  example,  there  is  a  well-known  reaction  by  which  aromatic 
amines  can  be  converted  into  the  corresponding  hydrocarbons.  It  would 
be  little  short  of  a  crime,  however,  except  for  academic  purposes,  to 
attempt  to  prepare  toluene  from  toluidine  in  this  way,  since  the  value  of 
the  finished  product  is  half  of  that  of  the  starting  material,  apart  altogether 
from  the  cost  of  the  other  reagents  required  ;  often  such  reactions  can 
well  be  studied  in  a  test-tube.  This  practical  application  of  a  very 
interesting  and  important  reaction  is  cited  merely  to  show  the  importance 
of  having  some  idea  of  the  cost  of  materials. 


6 


SYSTEMATIC  ORGANIC  CHEMISTRY 


This  should  be  done  in  all  the  simpler  preparations  which  are  likely  to 
be  included  in  any  price-list.  In  this  way  the  student  will  become  ac- 
quainted with  the  elements  of  costing  which  will  play  an  important  part 
in  his  after  life  in  the  factory,  where  economic  considerations  are  of  prime 
importance.  Even  should  he  not  take  up  the  manufacturing  side  of  his 
profession,  he  should  be  acquainted  with  the  relative  costs  of  the  more 
common  products,  and  trained  to  decide  for  himself  whether,  for  example, 
it  would  be  more  economical  to  extract  with  ether  or  benzene,  taking  into 
consideration  the  relative  efficiencies  of  the  two  processes. 

Moreover,  he  should  not  use  chemically  pure  products  for  his  pre- 
parations, unless  for  research  purposes.  The  ordinary  technical  qualities 
are  quite  suitable  for  most  preparations,  and  are,  of  course,  much  cheaper. 
It  should  be  remembered  that  the  facilities  for  the  purification  of  many 
organic  products  are  much  greater  on  the  large  scale,  than  in  the  laboratory. 
It  is,  however,  a  good  exercise  to  purify  for  himself  a  technical  product  of 
poor  quality  (see  Purification  of  Crude  Anthracene,  p.  171). 


CHAPTER  II 


APPARATUS  AND  METHODS 

Practical  Hints. 

Softening  of  Corks. — Corks  should  always  be  softened  before  inserting 
in  any  flask  and  the  boring  performed  after  softening.  Several  methods 
are  available.  The  cork  may  be  softened  in  the  ordinary  eccentric  iron 
press  between  the  two  rollers.  It  may  also  be  rolled  on  the  floor  under- 
neath the  foot.  A  convenient  way  is  to  place  the  cork  in  hot  or  boiling 
water  ;  the  cork  swells  somewhat  and  becomes  quite  soft  so  that  it  can 
be  made  to  fit  various  tubes  or  flasks.  An  excellent  method  of  reducing 
the  size  of  a  cork  is  to  rotate  it  in  a  flame  until  the  outer  coating  has  charred ; 
it  is  then  rolled,  and  cleaned  :  a  cork  thus  treated  may  be  used  for  vacuum 
distillations  as  the  layer  of  carbon  forms  a  good  seal. 

Rubber  stoppers  should  be  occasionally  rubbed  with  a  little  toluene, 
which  prevents  hardening  and  keeps  them  clean.  A  trace  of  vaseline 
smeared  on  a  rubber  stopper  affords  considerable  protection  from  the 
action  of  halogens.  Rubber  stoppers  should  always  be  removed  from 
vessels  while  the  latter  are  still  warm,  to  prevent  sticking  to  the  glass. 

Boring  of  Corks. — Sharp  borers  should  always  be  used.  The  end  of  the 
cork  is  placed  against  some  solid  object  and  bored  half-way  through  from 
one  end.  The  boring  should  then  be  completed  from  the  other  end.  The 
boring  of  rubber  stoppers  may  be  greatly  facilitated  by  moistening  the 
borer  with  caustic  soda. 

Removing  fixed  Stoppers. — Hot  water  should  be  run  on  to  the  neck  of 
the  bottle  and  the  stopper  gently  tapped  with  another  glass  stopper.  The 
neck  of  the  bottle  may  be  inverted  in  hot  water  for  a  minute  and  after- 
wards gently  tapped.  If  these  methods  fail,  and  if  the  contents  of  the 
bottle  are  not  easily  inflammable,  the  neck  of  the  bottle  may  be  rotated 
in  a  flame  prior  to  tapping.  Similar  methods  may  be  applied  to  fixed 
stop-cocks. 

Crystallisation. 

The  solid  product  obtained  from  a  chemical  reaction  is  seldom  pure, 
being  contaminated  with  various  impurities  and  by-products.  For 
purification,  the  process  of  crystallisation  is  generally  employed.  As  the 
process  is  of  such  frequent  occurrence,  the  student  should  early  in  his 
course  acquire  proficiency  in  it.  When  dealing  with  products  obtained 
in  plenty,  the  utmost  care  should  be  taken  to  obtain  the  maximum  yield 
of  pure  crystallised  compound,  as  only  by  doing  so  can  the  manipulative 
skill  be  acquired  which  is  necessary  to  obtain  a  satisfactory  yield  of  pure 
compound  from  a  product  obtained  in  meagre  quantities. 

7 


8 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Crystallisation  by  Cooling. — The  ideal  solvent  is  one  in  which  the  com- 
pound to  be  obtained  in  pure  crystalline  form  is  insoluble  in  the  cold,  but 
readily  soluble  in  the  hot.  Further,  the  impurities  should  either  be 
insoluble  or  else  very  soluble.  In  practice  such  a  solvent  is  seldom 
obtained,  but  the  nearest  approach  to  it  should  be  selected. 
The  solvents  most  commonly  employed  are  : — 

Water. 

Alcohol. 

Ether. 

Benzene. 

Petroleum  ether. 

Acetone. 

Glacial  acetic  acid. 

or  mixtures  of — 

Water  and  alcohol. 
Water  and  acetic  acid. 
Ether  and  petroleum  ether. 
Benzene  and  petroleum  ether. 

The  following  are  frequently  used  :  chloroform,  carbon  disulphide,  car- 
bon tetrachloride,  ethyl  acetate,  pyridine,  hydrochloric  acid,  sulphuric 
acid,  nitrobenzene,  aniline,  phenol,  epichlorhydrin,  ethylene  dichloride. 

Selection  of  Solvent. — In  order  to  select  a  suitable  solvent  small  quanti- 
ties (each  about  0-1  gm.)  of  the  finely  pulverised  product  are  placed  in 
several  test  tubes  and  treated  with  a  few  drops  of  single  solvents  of  the 
above  class.  Where  the  substance  dissolves  easily  in  the  cold  on  shaking, 
or  does  not  dissolve  appreciably  on  boiling,  the  solvents  in  question  may 
be  regarded  as  unsuitable.  Where  the  substance  dissolves  on  heating  or 
boiling,  and  separates  out  again  on  cooling,  the  solvents  are  suitable  ; 
that  solvent  should  be  selected  which  gives  good  crystals  in  the  greatest 
abundance.  At  times  crystallisation  does  not  take  place  owing  to  super- 
cooling ;  in  such  cases  the  side  of  the  test  tube  should  be  rubbed  with  a 
glass  rod,  or  the  solution  should  be  "  seeded  "  by  the  addition  of  a  small 
portion  of  the  crude  product,  since  such  operations  frequently  induce 
crystallisation.  If  necessary,  the  solution  should  also  be  cooled  in  ice  or 
in  a  freezing  mixture.  With  substances  which  are  sparingly  soluble  in 
the  common  solvents,  solvents  of  high  boiling  point  such  as  toluene,  nitro- 
benzene, etc.,  should  be  used. 

Where  no  single  solvent  is  found  suitable,  a  mixture  of  two  miscible 
solvents,  in  one  of  which  the  product  is  soluble  and  in  the  other  insoluble, 
may  be  employed  with  advantage.  Substances  which  are  very  soluble 
in  cold  alcohol  or  cold  acetic  acid  are  frequently  but  slightly  soluble  in 
water,  and  many  substances  which  are  very  soluble  in  benzene  are  sparingly 
soluble  in  petroleum  ether.  From  the  preliminary  investigation  with 
single  solvents  it  can  generally  be  deduced  which  are  suitable  to  serve  as 
mixed  solvents.  The  substance  is  dissolved  in  a  small  quantity  of  one 
solvent  and  heated  ;  the  second  solvent  is  then  gradually  added  to  the 
hot  solution  until  a  turbidity  appears  ;  heat  is  again  applied  until  com- 


APPARATUS  AND  METHODS 


9 


plete  solution,  takes  place,  and  the  solution  is  set  aside  to  cool.  Many 
substances  separate  in  an  amorphous  or  sticky  form  from  an  alcohol- water 
solvent.  It  is  important  that  the  crystals  should  be  sufficiently  well 
defined  that  their  crystalline  form  as  well  as  the  presence  of  other  crystals 
or  impurities  can  be  detected  with  the  aid  of  a  lens.  The  crystals  obtained 
from  these  preliminary  tests  should  be  preserved,  to  serve,  if  needed,  to 
"  seed  "  the  solution  containing  the  main  bulk  of  the  substance. 

Preparation  of  Solution. — If  the  substance  is  readily  soluble  the  heating 
is  generally  carried  out  in  a  flask  (conical  or  ordinary)  on  a  water  bath. 
If  considerable  heating  is  necessary,  a  reflux  condenser  should  be  provided 
to  avoid  loss  of  solvent  or  danger  of  fire.  Should  the  vapour  catch  fire, 
the  flame  should  be  withdrawn  and  the  mouth  of  the  vessel  covered  with 
a  damp  cloth  or  with  a  watch  glass.  When  the  solvent  is  neither  very 
volatile  nor  easily  inflammable  (i.e.,  water  or  acetic  acid),  the  heating 
may  be  performed  in  a  beaker  over  a  flame.  Small  quantities  of  such 
liquids  as  alcohol  or  benzene  may  be  heated  in  a  similar  manner  by  an 
experienced  operator.  Where  the  resulting  solution  does  not  require 
filtration,  a  conical  flask  should  always  be  used  (see  next  section).  During 
the  heating,  the  contents  of  the  vessel  should  be  fre- 
quently shaken  or  stirred,  since  crystals,  especially  when 
they  melt  to  a  heavy  oil  on  the  bottom  of  the  vessel, 
render  the  latter  liable  to  crack. 

In  preparing  the  solution  an  excessive  amount  of  sol- 
vent should  not  be  employed  at  first ;  successive  small 
quantities  should  be  added  to  the  boiling  or  nearly  boiling 
solution  until  the  substance  just  completely  dissolves,  or 
until  nothing  but  impurity  remains  undissolved.  With  fig.  1. 
substances  of  low  melting  point  care  should  be  taken  that 
concentrated  solutions  from  which  the  substance  commences  to  separate 
at  temperatures  above  its  melting  point,  are  not  used.  When  using 
mixed  solvents,  the  procedure  is  similar  to  that  described  for  the  pre- 
liminary tests  ;  if  on  the  addition  of  the  second  liquid  (i.e.,  water  or 
petroleum  ether)  resinous  impurities  separate,  these  should  be  filtered  off 
before  proceeding  further. 

Filtration  of  Hot  Solution  (see  also  Filtration).— This  operation  is  usually 
necessary  in  order  to  remove  insoluble  impurities,  filter  fibres,  etc.  When 
the  substance  does  not  separate  rapidly  from  the  hot  solution,  and  the 
liquid  filters  quickly,  the  solution  may  be  filtered  through  an  ordinary 
funnel  with  a  short  stem,  fitted  with  a  folded  filter  paper  (Fig.  1). 
Both  funnel  and  paper  should  previously  be  warmed  in  a  steam  bath. 
Or,  the  solution  may  be  filtered  with  suction,  using  suitable  types  of 
apparatus  (Figs.  26,  27).  The  funnel  and  filtering  medium  should  be 
previously  warmed.  When  the  filtrate  is  collected  in  a  thick  glass  suction 
flask,  the  latter  should  be  warmed  beforehand  by  immersion  in  warm 
water.  The  bell-jar  form  of  filtering  apparatus  (Fig.  28)  is  recommended, 
as  the  hot  solution  can  be  collected  in  a  conical  flask  of  suitable  size.  For 
"  crystallisation  by  cooling  "  a  rather  wide-mouthed  conical  flask  should 
be  used  to  contain  the  hot  filtered  solution — a  filter  flask  serves  equally 


10 


SYSTEMATIC  ORGANIC  CHEMISTRY 


well  for  large  volumes  ;  with  vessels  of  this  conical  type  the  crystals  do  not 
creep  up  the  sides,  as  may  occur  when  beakers  or  the  so-called  "  crystal- 
lisation dishes  "  are  used  ;  after  separation,  the  crystals  can  easily  be 
removed  with  the  aid  of  a  glass  rod  over  the  end  of 
which  a  short  piece  of  rubber  tube  has  been  drawn. 

If  the  substance  crystallises  rapidly  from  the  hot 
solution,  a  hot  filter  should  be  used.  Figs.  2  and  3 
show  steam  jacketed  and  hot- water  jacketed  filters. 
With  a  volatile  and  easily  inflammable  solvent  the 
flame  should  be  removed  from  the  jacket  immediately 
before  filtering,  danger  of  fire  being  thereby  avoided ; 
Fig.  2.  in  such  an  instance  the  steam  funnel  is  preferable 

when  the  steam  is  generated  at  a  safe  distance. 

After  nitration  the  conical  flask  is  covered  with  a 
watch-glass  and  set  aside.     If  large  crystals  are 
required,  the  rate  of  cooling  should  be  as  slow  as 
possible,  and  the  flask  should  not  be  disturbed.  The 
rate  of  cooling  may  be  lessened  by  immersing  the 
flask  in  a  bath  of  warm  water  and  allowing  the  bath 
[j        !  |       and  its  contents  to  cool.    If  the  substance  separates 
in  large  coarse  crystals  on  slow  cooling,  or  if  small 
pure  crystals  are  required,  it  is  expedient  to  cool 
quickly  in  cold  water  or  in  ice  water,  and  to  stir  or  agitate  the  solution  at 
the  same  time.    Small  crystals  are  generally  free  from  mother  liquor  which 
is  liable  to  be  occluded  in  large  crystals.    When  the  substance  is  very 
soluble  at  ordinary  temperature,  the  cooling  should  be  continued  in  a 
freezing  mixture. 


Cooling  Mixtures. 


Temp. 

Temp. 

Mixture  in  gms. 

falls  from 

Mixture  in  gms. 

falls  from 

15°  to 

15°  to 

14  alum  +  100  aq.  . 

14° 

25  amm.  chloride  +  100  ice 

—15° 

36  sodium  chloride  +  100  aq. 

13° 

45  amm.  nitrate  +  100  ice 

—17° 

12  pot.  sulphate  +  100  aq. 

12° 

50  sod.  nitrate  +  100  ice 

—18° 

14  sod.  phosphate  +  100  aq. 

11° 

33  sod.  chloride  +  100  ice 

—20° 

75  amm.  sulphate  +  100  aq. 

9° 

1  pot.  sulphocyanate  +  1  aq.  . 

—24° 

20  sod.  sulphate  cryst.  +  100  aq. 

8° 

52  amm.  nitrate  +  55 "] 

—26° 

85  mag.  sulphate  cryst.  +  100  aq. 

7° 

sod.  nitrate 

40  sod.  carbonate  cryst. +  100  aq. 

6° 

100  dil.  H2S04  66%  .  . 

—31° 

16  pot.  nitrate  +  100  aq.  . 

5° 

13  amm.  chloride  +  38  }  +100 

30  amm.  carbonate  +  100  aq. 

3° 

sod.  nitrate    .     .  1  ice. 

—31° 

30  calcium  chloride  +  100  aq.  . 

2° 

2  pot.  nitrate  +  112  | 

20  sod.  carbonate  +  100  ice 

 2° 

pot.sulphocyanate  J 

—34° 

30  amm.  chloride  +  100  aq. 

—3° 

3  calcium  chloride  cryst.  +  2  ice 

—49° 

110  sod.  thiosulphate  +  100  aq.  . 

—4° 

Solid  C02  +  ether 

—100° 

250  calcium  chloride  cryst.  + 100  aq . 

—8° 

30  pot.  chloride  +  100  ice 

—11° 

100  cone.  HC1  +  100  ice  . 

—  15° 

8  sod.  sulphate  +  5  cone.  HC1  . 

—12° 

50  cone.  HC1  +  100  ice  . 

-18° 

From  Erdrnann-Kothner — N aturkonstanten  (1905). 


APPARATUS  AND  METHODS 


1 1 


Separation  of  Crystals.— This  is  generally  effected  by  filtration  with 
suction,  vessels  of  size  suitable  to  the  quantities  dealt  with  being  selected. 
The  crystals  left  on  the  funnel  should  be  well  pressed  down  and  then 
washed  a  few  times  with  small  quantities  of  the  pure  solvent  in  order  to 
remove  the  last  traces  of  mother  liquor.  If  the  substance  is  easily  soluble, 
too  large  quantities  of  solvent  must  not  be  employed  for  washing.  When 
a  solvent  which  is  not  readily  volatile  has  been  used  (e.g.,  nitrobenzene, 
acetic  acid,  etc.),  it  must  be  removed  from  the  crystals  by  washing  with 
an  easily  volatile  solvent  with  which  it  is  miscible.  After  being  thoroughly 
drained  on  the  funnel,  the  crystals  are  dried  (see  also  p.  33).  They 
may  be  placed  on  filter  paper  or  porous  plate,  covered  to  protect  from 
dust,  and  allowed  to  dry  in  the  air,  or  left  in  a  desiccator  over  a  suitable 
substance  to  absorb  the  solvent ;  the  operation  may  be  hastened  by 
evacuating  the  desiccator.  If  the  crystals  have  a  high  melting  point,  the 
drying  may  be  effected  in  a  bath  at  temperatures  below  the  fusion  point. 
In  this  connection  it  should  be  noted  that  the  presence  of  small  quantities 
of  solvent  may  produce  a  considerable  lowering  of  the  melting  point — to 
avoid  this  a  test  portion  should  first  be  dried. 

Often  further  crops  of  crystals  can  be  obtained  by 
concentrating  the  mother  liquor  ;  generally  these  are 
less  pure  and  require  to  be  recrystallised.  In  some 
cases  the  first  crop  has  to  be  recrystallised  before  the 
crystals  are  pure  (determined  by  M.P.).  It  is  often 
convenient,  in  order  to  separate  a  second  crop,  to 
dilute  the  mother  liquor  with  a  liquid  in  which  the  dis- 
solved substance  is  sparingly  soluble.  Crops  separated 
in  this  wTay  generally  require  recrystallisation. 

Crystals  which  are  very  soluble  in  the  solvent  at  laboratory  temperature, 
and  which  have  been  obtained  by  cooling  the  solution  in  a  freezing  mixture, 
should  be  filtered  through  an  ice-jacketed  funnel  (Fig.  4). 

In  all  cases  the  process  of  crystallisation  must  be  continued  until  no 
change  in  melting  point  occurs  on  further  crystallisation,  or  until  the 
product  obtained  by  evaporating  a  sample  of  the  mother  liquor  has  the 
same  melting  point  as  the  crystals  separated  from  it. 

Crystallisation  by  Evaporation. — This  method  is  employed  when  the 
substance  is  so  easily  soluble  in  all  solvents  (hot  and  cold)  that  it  will  only 
separate  after  partial  evaporation.  The  solvent  is  allowed  to  evaporate 
spontaneously  in  the  air  or  in  a  desiccator  ;  if  in  the  latter  the  evaporation 
is  greatly  hastened  by  using  a  suitable  absorbent  as  well  as  evacuating  the 
desiccator.  The  type  of  vessel  employed  depends  on  the  volatility  of  the 
solvent ;  obviously  the  conical  flask  already  recommended  for  "  crystal- 
lisation by  cooling  "  is  not  suitable  for  spontaneous  evaporation,  while  a 
beaker  or  shallow  "  crystallising  dish  "  is.  When  the  latter  type  of 
vessel  is  used,  "  crusts  "  often  form  on  the  sides  above  the  surface  of  the 
liquid.  Such  crusts  seldom  consist  of  pure  substance,  and  they  should  be 
carefully  removed  with  a  spatula  before  attempting  to  filter  off  the 
crystals. 

Since  the  purifying  effect  of  crystallisation  depends  on  the  fact  that  the 


12 


SYSTEMATIC  ORGANIC  CHEMISTRY 


impurities  remain  dissolved  in  the  mother  liquor — except  in  cases  where 
the  impurities  being  insoluble  are  first  filtered  of! — the  solvent  should 
never  be  completely  evaporated,  but  the  crystals  should  be  filtered  of! 
while  still  covered  with  mother  liquor. 

Special  Methods. — With  some  substances  it  is  difficult  to  obtain  good 
crystals  by  the  methods  already  described.  A  method  which  frequently 
gives  excellent  results,  consists  in  dissolving  the  substance  in  some  solvent, 
then  adding  a  second  solvent,  miscible  with  the  first,  but  in  which  the 
substance  is  sparingly  soluble.  The  first  solvent  is  then  gradually  removed 
and  the  substance  separates  out — usually  in  the  crystalline  form.  If  the 
first  solvent  is  the  more  volatile  in  air,  spontaneous  evaporation  in  air  may 
diminish  its  concentration  in  the  solution.  The  solution  may  be  placed 
in  a  desiccator  over  some  substance  which  absorbs  the  first  solvent  but  not 
the  second  ;  in  this  way  water  may  be  removed  from  a  water-alcohol 
solution  by  solid  caustic  potash  or  quicklime. 

Another  method — applicable  when  the  substance  is  soluble  in  alcohol 
and  in  ether,  but  insoluble  in  water — consists  in  making  a  saturated  solu- 
tion in  cold  alcohol,  adding  water  until  considerable  precipitation  has 
taken  place,  then  adding  ether  until  the  precipitate  has  redissolved,  and 
finally  allowing  the  ether  to  diminish  by  spontaneous  evaporation. 

When  a  substance  is  soluble  without  change  in  concentrated  sulphuric 
acid,  but  insoluble  in  water,  a  saturated  solution  in  the  former  medium 
when  left  exposed  to  water- vapour — say,  side  by  side  with  a  vessel  of  water 
under  a  bell- jar — gradually  absorbs  water,  and  the  substance  frequently 
separates  out  in  crystalline  form. 

The  purification  of  many  products  can  be  facilitated  by  distillation, 
prior  to  crystallisation,  provided  they  distil  without  decomposition. 
Generally  it  is  preferable  to  conduct  the  distillation  under  reduced  pressure. 

Fractional  Crystallisation. 

The  process  of  fractional  crystallisation  is  employed  to  separate  two  or 
more  substances,  all  of  which  are  soluble  in  the  solvent  used.  When  only 
two  substances  are  present,  it  is  often  possible  to  find,  by  preliminary  tests, 
a  solvent  which,  when  used  in  suitable  quantity,  will  dissolve  the  whole  of 
the  more  soluble  compound,  but  only  a  small  quantity  of  the  less  soluble. 
In  such  a  case,  a  preliminary  separation  may  be  effected  by  shaking  the 
mixture  with  a  quantity  of  solvent  (hot  or  cold — as  found  suitable  by 
trial),  and  filtering  the  solution  from  the  residue  remaining  undissolved. 
For  extracting  a  mixture  of  this  nature  with  a  hot  solvent  the  Soxhlet 
apparatus  (Fig.  29)  is  specialty  useful ;  in  fact  this  apparatus  should  be 
employed  for  all  extractions  where  a  residue  remains  undissolved,  since 
filtration  as  well  as  extraction  is  accomplished  ;  also  only  a  relatively 
small  quantity  of  solvent  is  required  (see  p.  31). 

When  commencing  a  fractional  crystallisation,  preliminary  tests  similar 
to  those  described  under  "Crystallisation"  are  first  carried  out,  and 
the  crystals  which  separate  during  such  tests  examined  with  a  lens.  The 
crystals  which  form  first  are  either  the  least  soluble  or  most  abundant 
constituent  of  the  mixture.    If  a  second  or  further  type  of  crystal  appears, 


APPARATUS  AND  METHODS 


L3 


its  shape  and  time  of  formation  relative  to  cooling  should  be  noted  ;  it  is 
often  necessary  to  filter  off  the  first  crop  while  the  mixture  is  still  warm. 

When  dealing  with  a  finely-powdered  or  amorphous  mixture,  it  is  often 
useful  to  examine  a  small  portion  placed  on  a  watch-glass  under  the 
microscope.  The  action  of  a  few  drops  of  various  solvents  (hot  or  cold) 
can  be  examined  in  this  position,  and  valuable  information — which  might 
not  be  obvious  to  the  naked  eye — perhaps  gained  concerning  the  solubility 
or  insolubility  of  some  constituent  in  a  particular  solvent. 

No  definite  plan  can  be  given  which  will  suit  all  examples  of  fractional 
crystallisation.  The  scheme  outlined  in  "  Text-book  of  Inorganic 
Chemistry,"  Vol.  IV.,  p.  324  (J.  Newton  Friend),  when  applicable,  affords 
a  convenient  method  of  marking  and  recording  the  various  fractions 
involved  in  a  fractional  crystallisation  ;  it  also  avoids  the  accumulation 
of  a  vast  number  of  small  crops  and  mother  liquors  : — 


The  mixture  is  dissolved  with  the  aid  of  heat  in  a  solvent  to  give  solu- 
tion (1).  From  this  solution  on  cooling,  crystals  separate  which  are 
filtered  off,  and  solution  (1)  is  thereby  divided  into  crop  (2)  and  mother 
liquor  (3).  Crop  (2)  is  dissolved  in  the  minimum  quantity  of  hot  solvent, 
and  from  the  resulting  solution  after  cooling,  crop  (4)  and  mother  liquor  (5) 
are  obtained.  Mother  liquor  (3)  is  concentrated,  and  from  the  concen- 
trated solution  after  cooling,  crop  (6)  and  mother  liquor  (7)  are  obtained. 
Crop  (6)  and  mother  liquor  (5)  are  united  to  form  a  single  fraction,  and 
after  being  heated  to  dissolve  and  subsequently  cooled  give  rise  to  crop  (10) 
and  mother  liquor  (11).  Crop  (4)  is  dissolved  in  a  small  portion  of  pure 
solvent  by  heating  and  after  cooling  is  divided  into  crop  (8)  and  mother 
liquor  (9).  Mother  liquor  (7)  after  concentration  and  cooling  yields  crop 
(12)  and  mother  liquor  (13).  (9)  and  (10),  likewise  (11)  and  (12),  are 
united  to  give  single  fractions.    Proceeding  in  this  way,  the  least  soluble 


14 


SYSTEMATIC  ORGANIC  CHEMISTRY 


compound  goes  to  the  left  in  the  diagram,  while  the  most  soluble  goes  to 
the  right,  and  compounds  of  intermediate  solubility  lie  between  these 
extremes.  Each  crop  should  be  tested  for  purity.  If,  when  examined 
with  the  aid  of  a  lens,  two  or  more  types  of  crystals  are  present,  the  crop 
must  be  recrystallised.  When  a  crop  appears  uniform,  a  small  portion 
should  be  withdrawn,  dried  by  exposure  on  porous  porcelain  or  on  filter 
paper,  and  its  melting  point  taken.  In  the  above  scheme  if  crop  (2),  say,  is 
pure  it  takes  no  further  part  in  the  recrystallisation  ;  mother  liquor  (3)  is 
then  worked  up.  When  the  principal  product  is  moderately  soluble  in  the 
hot  solvent,  but  not  very  soluble  in  the  cold  solvent,  the  following  method 
might  be  serviceable.  The  product  is  divided  into  three  (say)  equal  por- 
tions, A,  B  and  C.  A  is  recrystallised  from  the  minimum  quantity  of  pure 
solvent,  yielding  crop  Av  The  mother  liquor  from  Ax  and  small  quantity 
of  washings  are  used  to  recrystallise  B,  yielding  crop  Bx.  The  mother 
liquor  from  B1  is  similarly  used  to  recrystallise  C.  In  this  way  the  mother 
liquor  from  Cx  should  be  more  or  less  saturated  with  the  impurities 
present,  while  it  contains  but  little  more  of  the  principal  product  than 
was  contained  in  the  mother  liquor  from  Ar  If  crop  Ax  is  impure,  it  is 
recrystallised  from  fresh  solvent  yielding  crop  A2.  Crops  Bx  and  Cx  are 
recrystallised  from  mother  liquors  A2  and  B2,  and  mother  liquors  Cx  and 
C2  are  united.  The  process  is  continued  after  this  fashion  until  the  crop 
under  A  is  pure.  The  crop  under  B  then  becomes  the  first  fraction,  and 
the  mother  liquors  from  the  C's  are  combined  and  evaporated  so  as  to 
give  a  crop  D,  which  becomes  the  new  end-fraction  and  enters  into  the 
recrystallisations  : — 


A 

B 

C 

Ai 

Bi 

Ci 

An 

Bn 

Cn 

D 

Bm      Cm      Dm— n  E 


This  method  was  found  very  useful  for  the  purification  of  ^-a-phenyl- 
ethylamine  Z-malate  (p.  401). 

When  the  product  separates  from  the  solvent  in  compact  crystalline 
masses,  the  mother  liquor  may  be  decanted  on  to  the  next  fraction,  and 
thus  filtration,  which  is  always  attended  with  some  slight  loss  of  material, 
is  avoided. 

It  sometimes  happens  that  after  a  fractional  crystallisation  has  been 
continued  for  some  time,  a  solution  is  obtained  from  which  two  products 
crystallise  side  by  side,  the  solution  being  apparently  saturated  with 
regard  to  each  product.  In  such  a  case  a  separation  might  be  effected  by 
evaporating  off  the  solvent  and  proceeding  with  a  different  solvent  in 
which  the  ratio  of  the  solubilities  of  the  two  compounds  differs  from  the 
corresponding  ratio  in  the  first  solvent.    In  some  such  cases  mechanical 


APPARATUS  AND  METHODS 


15 


means  of  separation  might  be  effective  ;  if  one  set  of  crystals  is  heavier 
than  the  other,  the  lighter  set  may  be  separated  by  stirring  the  super- 
natant liquor  (or  by  rotating  the  vessel)  and  rapidly  decanting.  The 
mother  liquor  after  nitration  from  the  lighter  crystals  may  be  agitated  a 
second  time  over  the  heavier  crystals  in  order  to  remove  any  of  the  lighter 
which  still  remain.  If  one  or  both  sets  of  crystals  separate  in  fairly  large 
form,  a  separation  may  be  effected  by  hand  picking. 

Determination  o£  Melting  Point. 

In  order  to  identify  a  substance,  or  to  test  its  purity,  the  melting  point 
of  the  substance  is  determined,  a  process  which  can  be  rapidly  carried  out. 
If  a  substance  does  melt  at  all,  it  should,  if  pure,  melt  sharply  at  a  definite 
temperature.  If  the  aim  is  one  of  final  identification  of  the  compound, 
this  figure  should  agree  with  the  figure  given  in  the  literature.  If  the 
figure  is  considerably  lower  than  the  one  given,  one  must  suspect  impurity 
or  else  a  different  compound  from  that  stated.  In  every  case,  however, 
the  melting  point  should  be  verified  by  reference  to  Beilstein  or  Richter's 
Lexicon  or  Stelzner.  If  the  melting  point  is  higher  than  the  figure  given, 
the  compound  may  be  a  different  one,  or  the  melting  point  may  have  been 
carelessly  taken,  for  example,  by  heating  too  quickly.  In  general,  a  pure 
substance  melts  within  1°  of  the  figure  given.  If  the  melting  point  is  not 
sharp,  the  substance  should  be  recrystalHsed  from  a  suitable  solvent  before 
a  further  determination  is  made.  From  this  it  is  obvious  that  great  care 
should  be  observed  in  making  this  simple  determination,  and  the  following 
points  should  be  carefully  observed. 

The  choice  of  a  thermometer  is  an  important  one.  In  the  first  place  it 
should  have  a  small  bulb,  and  the  range  should  be  suitably  chosen.  For 
example,  if  it  is  known  that  a  substance  has  a  low  melting  point,  a  ther- 
mometer of  range  0° — 100°  should  be  used.  If  the  substance  has  a  high 
melting  point,  a  range  of  say  200° — 300°  should  be  chosen  and  so  on.  All 
thermometers  used  for  the  determination  of  melting  points  should  be 
standardised  against  a  standard  thermometer. 

The  preparation  of  the  capillary  tube  requires  a  little  practice.  A  piece 
of  thin- walled  glass  tubing  or  a  test  tube  is  heated  in  an  ordinary  Bunsen 
flame  or  blow-pipe  until  it  softens,  when  it  is  withdrawn  from  the  flame 
and  carefully  drawn  out  for  2  or  3  feet.  Draw  slowly  at  first,  then  quicker 
as  the  glass  cools  and  hardens.  The  central  part,  consisting  of  the  capillary 
tube,  is  then  cut  into  sections  of  about  8 — 10  cms.  in  length,  and  one  end 
of  each  section  fused  in  the  flame.  A  supply  of  melting  point  tubes 
should  always  be  in  readiness. 

The  substance  of  which  the  melting  point  has  to  be  taken  should  be 
perfectly  dry.  A  sample  is  ground  to  a  fine  powder  on  a  watch-glass  with 
a  clean  glass  rod,  introduced  into  the  capillary  tube  and  shaken  to  the 
bottom,  light  scratching  of  the  tube  with  a  file  often  brings  this  about. 
The  tube  is  then  ready  for  fixing  to  the  thermometer.  The  liquid  used  in 
the  melting  point  apparatus  is  usually  concentrated  sulphuric  acid 
(vaseline  may  also  be  used).    After  being  reheated  several  times,  sulphuric 


16 


SYSTEMATIC  ORGANIC  CHEMISTRY 


acid  is  apt  to  become  discoloured.  It  may  be  rendered  water-white  again 
by  adding  a  crystal  of  potassium  nitrate  and  heating.  For  melting  points 
above  250°  sulphuric  acid  should  not  be  employed  alone.  For  melting 
points  ranging  between  250° — 350°  C,  about  30%  of  potassium  sulphate 
should  be  added  to  the  sulphuric  acid.  Higher  temperatures  may  be 
obtained  by  increasing  the  quantity  of  potassium  sulphate.  This  sulphate 
mixture  is  solid  at  ordinary  temperature,  but  it  is  not  so  easily  discoloured. 
For  temperatures  above  370°  fused  zinc  chloride  may  be  used  in  place  of 
sulphuric  acid  or  the  sulphate  mixture. 

The  melting  point  apparatus  consists  of  a  small  beaker  or  a  large-sized 


Fig.  5.  Fig.  6. 


test  tube  containing  sulphuric  acid  up  to  a  convenient  level.  The  ther- 
mometer can  be  held  in  position  with  its  bulb  well  immersed  in  the  acid, 
by  means  of  a  clamp  in  the  former  case,  or  by  means  of  a  cork  in  the  latter. 
It  is  advisable  to  have  some  kind  of  mechanical  agitation  in  the  sulphuric 
acid  (see  sketch)  although  if  the  heating  is  carefully  done,  this  may  be 
dispensed  with. 

Figs.  5  and  6  show  the  arrangement  in  the  two  cases  where  a  glass 
rod  is  used  as  a  stirrer,  the  stirring  being  maintained  while  the  acid  is 
slowly  heated.  The  cork  at  A  in  Fig.  6  should  be  as  thin  as  possible 
so  as  to  obscure  the  minimum  amount  of  the  scale,  and  if  no  agitator  is 
used  passing  through  the  cork,  then  a  slit  should  be  made  in  the  cork  to 
allow  exit  to  the  vapours  on  heating. 

The  thermometer  is  first  dipped  in  the  sulphuric  acid,  and  then  the  drop 


APPARATUS  AND  METHODS 


17 


of  acid  which  clings  to  the  bulb  is  smeared  on  the  side  of  the  capillary  tube 
containing  the  substance.  The  capillary  tube  is  then  made  to  adhere  to 
the  thermometer  (Fig.  6)  by  capillary  attraction,  so  that  the  substance  in 
the  tube  is  just  opposite  the  bulb  of  the  thermometer.  This  method  is  much 
better  than  using  a  rubber  band,  which  is  apt  to  perish  in  the  sulphuric  acid 
fumes,  and  gives  rise  generally  to  a  speedy  discoloration  of  the  acid. 

A  cloth  should  be  placed  on  the  bench  below  the  apparatus  when  heating 
is  commenced,  so  as  to  protect  the  observer  should  an  accident  occur. 
The  Bunsen  burner  should  be  held  in  the  left  hand  and  the  stirrer  worked 
with  the  right.  The  heating  should  be  moderated  on  approaching  the 
melting  point,  and  the  Bunsen  lowered  to  give  a  flame  about  2  cms.  in 
length.  The  temperature  at  which  the  substance  shows  the  "first  sign  of 
melting  is  taken  as  the  melting  point  of  the  substance. 

Correction. — Melting  points  are  usually  given  as  "  uncorrected  "  ;  for 
correction  the  following  formula  is  employed  : — 

Tc  =  T0  +  0-000156Z(To  -  Tm) 
Tc  =  corrected  temperature. 
T0  =  observed  temperature. 
0-000156  =  apparent  coefficient  of  expansion  of  mercury  in  glass. 

I  =  length  of  mercury  column  in  degrees  above  surface  of  liquid. 
Tm  =  mean  temperature  of  mercury  column,  i.e.,  the  temperature 
of  the  middle  point  of  the  mercury  column,  taken  by 
another  thermometer. 

Some  Corrected  Melting  Points  for  Standardising  Thermometers. — 

p-Toluidine    ...      45°  Salicylic  acid  .  .  .  159-8° 

a-Naphthylamine   .        .       50°  Anthracene    .  .  .  216° 

Naphthalene  .       .       .      80-8°  Carbazole      .  .  .  246° 

Benzoic  acid  .       .       .  122-5°  Anthraquinone  .  .  285° 

"Mixed"  Melting  Points. — Impurities  generally  lower  the  melting 
point  of  a  substance.  To  determine  whether  two  substances  of  the  same 
melting  point  are  one  and  the  same,  a  convenient  method  is  to  mix  equal 
quantities  of  the  two  and  take  a  melting  point  of  the  mixture.  If  the 
melting  point  is  not  lowered  the  two  substances  are  identical. 

Setting  Point. — When  a  large  quantity  of  the  substance  is  available  a 
very  speedy  determination  of  its  setting  point  (freezing  point)  may  be 
made  as  follows.  The  method  is  used  largely  on  the  technical  scale,  and 
is  specially  suitable  for  controlling  chemical  operations. 

The  substance  is  placed  in  a  large  test  tube  and  melted.  A  thermometer 
reading  fifths  or  tenths  of  a  degree  is  used,  and  is  placed  in  the  melted 
substance  which  is  stirred  by  means  of  the  thermometer.  The  mercury 
in  the  thermometer  gradually  falls  as  the  liquid  cools,  until  it  reaches  a 
point  when  it  jumps  up  suddenly  (due  to  the  heat  liberated  on  the  appear- 
ance of  the  solid  phase).  The  stirring  is  continued,  and  the  highest 
temperature  to  which  it  reaches  after  this  upthrust  is  taken  as  the  setting 
point  or  freezing  point.  This  figure  should,  of  course,  agree  with  the 
melting  point. 


18  SYSTEMATIC  ORGANIC  CHEMISTRY 

Distillation  and  Determination  of  Boiling  Point. 

The  apparatus  for  the  ordinary  distillation  of  a  liquid  and  for  deter- 
mining its  boiling  point  is  the  same.    A  pure  liquid  should  boil  at  a 


{a)  For  low  B.P.  liquids.      (6)  For  medium  B.P.  liquids,    (c)  For  high  B.P.  liquids. 

Fig.  7. 

constant  temperature,  and  the  whole  should  pass  over  within  a  very 
small  range. 

The  liquid  to  be  distilled,  or  of  which  the  boiling  point  is  to  be  obtained. 


Fig.  8. 


is  placed  in  a  suitable  round-bottomed  flask,  fitted  with  a  side  tube.  The 
flask  chosen  should  be  of  suitable  capacity,  e.g.,  one  should  not  use  a 
500-c.c.  distilling  flask  to  distil  10  c.cs.  of  a  liquid.  Figure  7  above  shows 
the  position  the  side  tube  should  hold  in  particular  cases. 


APPARATUS  AND  METHODS 


L9 


This  is  important,  and  a  proper  choice  will  well  repay  the  trouble  taken. 

The  liquid  should  half  fill  the  bulb  of  the  distilling  flask. 

Determination  of  Boiling  Point. — After  the  liquid  has  been  placed  in  the 
distilling  flask,  the  thermometer  which  is  chosen  to  suit  the  substance,  as 
in  the  determination  of  melting  points,  is  fixed  in  the  neck  of  the  flask  by 


Fig.  9. 


means  of  a  thin  cork,  so  that  the  bulb  of  the  thermometer  is  opposite  the 
exit  tube. 

The  flask  is  then  fixed  to  a  condenser  by  means  of  a  cork  placed  as  near  as 
possible  to  the  neck  of  the  flask.  The  condenser  is  attached  to  an  adapter 
at  its  lower  end  to  deliver  the  condensed  liquid  into  a  receiver.  This  cork 
should  be  placed  as  far  as  possible  from  the  end  of  the  condenser  tube. 
The  sketch.  (Fig.  8)  shows  how  the  complete  apparatus  should  appear. 
The  ordinary  Liebig  condenser  should  be  replaced 
by  an  air  condenser  for  liquids  boiling  over  160° 
(see  Fig.  9). 

When  inflammable  liquids  are  distilled,  the 
receiver,  as  shown,  should  take  the  form  of  a 
Buchner  flask,  with  a  rubber  tube  connected  to 
the  side  tube,  and  dipping  over  the  side  of  the 
bench.  In  this  way  inflammable  vapours  are 
removed  from  the  region  of  the  Bunsen  burner. 

Before  heating  is  commenced,  a  small  piece  of 
unglazed  porcelain  or  magnesite  is  introduced 
into  the  flask  in  order  to  prevent  "  bumping  "  or 
j  too  vigorous  boiling.  Heat  is  applied  very 
gradually,  and  the  temperature  raised  very  slowly  at  first,  until  it  reaches  a 
point  at  which  the  liquid  distils  regularly  and  there  remains  constant. 
,  This  temperature  is  the  boiling  point  of  the  liquid. 

When  there  is  only  a  very  small  quantity  of  liquid  available,  two 
methods  may  be  applied  : — 

1.  A  very  small  distilling  flask,  preferably  pear-shaped,  may  be  used. 
The  sketch  (Fig.  10)  shows  a  very  useful  type  of  flask  for  this  purpose. 

c  2 


20 


SYSTEMATIC  ORGANIC  CHEMISTRY 


These  flasks  can  be  obtained  of  capacity  down  to  1  c.c.  The  hood  prevents 
condensed  liquid  returning  to  the  bulb. 

2.  This  jnethod_  may  be  employed  for  even  one  drop  of 
liquid.  The  latter  is  placed  in  a  narrow  tube  which  has  been 
sealed  at  one  end,  and  this  tube  is  attached  to  a  thermometer 
by  means  of  a  rubber  band  in  such  a  position  that  the  liquid 
is  opposite  the  bulb  of  the  thermometer.  Into  the  liquid  is 
now  placed  the  open  end  of  a  sealed  melting  point  tube  ;■ 
the  whole  is  fixed  in  the  melting  point  apparatus.  The 
sketch  (Fig.  11)  shows  the  arrangement. 

At  first  bubbles  of  air  are  expelled  from  the  end  of  the 
capillary  tube  due  to  expansion  as  soon  as  heat  is  applied 
to  the  acid  ;  the  heating  should  be  very  carefully  carried  out. 
Ultimately  a  point  will  be  reached  at  which  there  is  a  regular 
I   stream  of  bubbles  emitted  from  the  tube.    This  temperature 
is  the  boiling  point.    At  least  two  observations  should  be 
Fig.  11.     niade  by  this  method,  a  new  capillary  tube  being  used  each 
time.    The  mean  is  taken  as  the  true  boiling  point.  These 
boiling  points  are  "  uncorrected  " — the  "  corrected  "  figure  is  obtained  as 
with  melting  points. 

Corrections. — {a)  Thermometer  Reading. 

Tc  =  T0  +  0-000156Z(To  -  Tm) 
T0  =  observed  boiling  point. 
Tc  =  corrected  boiling  point. 
I  =  length  of  mercury  column  not  heated  by  the  vapours. 
Tm=  mean  temperature  of  mercury  column  (see  Melting  Point). 

(b)  Barometric  Pressure. 

Tc  =  TG  +  0-043  (760  -  P) 
P  =  atmospheric  pressure  in  millimetres. 


Some  Corrected  Boiling  Points  for  Standardising  Thermometers.— 

Chloroform    .  .  .  61-3°  Nitrobenzene  .  .  .  210-9° 

Benzene        .  .  .  80-2°  Quinoline       .  .  .  237-5° 

Chlorobenzene  .  .  131-2°  Benzophenone  .  .  305-9° 

Aniline          .  .  .  184-4°  Mercury        .  .  .  356-8° 


Fractional  Distillation. 

Fractional  distillation,  using  the  ordinary  distillation  apparatus,  is 
employed  for  separating  substances  whose  boiling  points  differ  by  at  least 

40°  C.    The  mixture  is  distilled  slowly  and  the  distillates  are  collected  in  i 

separate  receivers.    For  example,  a  mixture  of  benzene  (B.P.  80-2°)  and  1 

nitrobenzene  (B.P.  210-9°)  can  be  separated  by  collecting  the  distillate  i 

which  came  over  at  about  80°  in  one  receiver  and  the  distillate  which  came  1 

over  at  about  210°  in  another  receiver.    By  repeating  this  process  carefully,  \ 

the  two  receivers  will  ultimately  contain  pure  benzene  and  pure  nitro-  r 


APPARATUS  AND  METHODS 


2) 


benzene  respectively.  It  is  always  necessary  to  repeat  the  process  when 
the  boiling  points  of  the  liquids  are  fairly  close. 

When  the  boiling  points  lie  near  one  another  the  same  method  can  be 
used,  but  before  a  separation  can  be  obtained  the  process  may  have  to  be 
repeated  ten  or  twenty  times,  and  even  then  the  separation  will  probably 
not  be  complete.  By  using  still-heads  or  fractionating  columns  this 
difficulty  can  be  obviated.  Fig.  12  indicates  the  types  of  still-heads 
most  commonly  used  in  the  laboratory  for  this  purpose.  The  principle  of 
all  is  similar  ;  they  offer  a  large  cooling  surface  to  the  rising  vapours  which 
are  always  in  contact  with  the  falling  condensed  liquid.   In  this  way  only 


Fig.  12.  Fig.  13. 


the  more  volatile  liquid  passes  over  to  the  condenser.  Fig.  13  shows  a 
column  attached  to  a  flask.  Such  an  apparatus  could  be  used  for  separat- 
ing, say,  a  mixture  of  benzene  (B.P.  80-2°)  and  toluene  (B.P.  110°).  It  is 
always  necessary  to  repeat  the  process  at  least  once  until  the  constituents 
of  the  mixture  give  definite  boiling  points. 

In  some  cases  liquids,  even  with  different  boiling  points,  cannot  be 
separated  in  this  way,  owing  to  the  formation  of  constant  boiling  mixtures, 
which  behave  like  pure  substances.  The  boiling  point  of  such  a  mixture 
is  a  function  of  the  pressure.  Such  mixtures  cannot,  therefore,  be  separated 
by  distillation.  The  excess  of  each  constituent  beyond  the  constant 
boiling  proportion  would,  of  course,  pass  over,  until  the  composition 
reached  that  of  the  constant  boiling  mixture,  which  has  either  a  maximum 


22 


SYSTEMATIC  ORGANIC  CHEMISTRY 


or  minimum  boiling  point  compared  with  any  other  mixture  of  the 
substances. 

The  tables  given  below,  which  are  taken  from  "  A  Laboratory  Course  of 
Organic  Chemistry  "  (A.  W.  Titherley),  show  the  boiling  point  and  com- 
position of  some  such  constant  boiling  mixtures,  consisting  of  two  sub- 
stances, A  and  B. 

Constant  Boiling  Mixtures. 


Minimum  B.P.    Type  I. 


A. 

B. 

B.P.  of 
constant 
mixture . 

%  of  A.  in 
constant 
mixture. 

B.P. 

B.P. 

Methyl  alcohol  . 

65-5° 

Acetone 

56-6° 

55-95° 

13-5 

Water 

100° 

Ethyl  alcohol 

78-3° 

78-15° 

4-43 

Water 

100° 

Isopropyl  alcohol  . 

82-45° 

80-35° 

12-10 

Water 

100° 

n  -Propyl  alcohol  . 

97-2° 

87-7° 

28-31 

Water 

100° 

Butyric  acid 

159-5° 

99-2° 

80 

Benzene  . 

80-2° 

Ethyl  alcohol 

78-3° 

68-25° 

67-64 

Benzene  . 

80-2° 

Methyl  alcohol 

65-5° 

58-35° 

60-45 

Pyridine  . 

115° 

Water  . 

100° 

92-5° 

59 

laximum  B.P.    Type  II. 

Water 

100° 

Formic  acid  . 

99-9° 

1071° 

23 

Water 

100° 

HC1     .        .  about 

-80° 

110° 

79-76 

Water 

100° 

HBr     .        .  „ 

-73° 

126° 

52-5 

Water 

100° 

HI               .  „ 

-35° 

127° 

43 

Water 

100° 

HN03  . 

86° 

120-5° 

32 

Chloroform 

61-2° 

Acetone 

56-6° 

64-7° 

80 

The  boiling  points  are  given  for  760  mms.  pressure.  In  Type  I.  the  boil- 
ing point  of  the  constant  boiling  mixture  is  below  that  of  either  con- 
stituent, while  in  Type  II.  the  boiling  point  of  the  constant  boiling  mixture 
is  above  that  of  either  constituent. 

References. — For  theoretical  considerations  of  this  subject  the  student 
is  referred  to  : — 

Walker,  "  Introduction  to  Physical  Chemistry"  (1919),  p.  83. 
Smith,  "  Introduction  to  Inorganic  Chemistry,"  pp.  587,  609,  211, 
273,  279. 

Noyes  and  Warfel,  Am.  Soc,  23  (1901),  468. 
Young,  "  Stoichiometry  "  (1918),  p.  252. 
A  very  simple  and  ingenious  type  of  still-head,  and  one  which  is  very 
effective,  was  patented  by  Dufton  (see  J.  S.  C.  L,  38,  45). 

Steam  Distillation. 

Steam  distillation  is  sometimes  employed  for  separating  substances  of 
high  boiling  point  which  have  an  appreciable  vapour  pressure  at  100°.  It 


APPARATUS  AND  METHODS 


23 


consists  in  passing  a  current  of  steam  through  the  mixture.  The  sketch 
(Fig.  14)  shows  the  apparatus  usually  employed.  The  steam  is  generated 
in  a  tin  canister  or  a  glass  flask  which  is  provided  with  a  long  glass  safety 


Fig.  14. 

tube  dipping  below  the  surface  of  the  water.  The  distilling  flask  should 
be  large  and  should  be  sloped  to  prevent  the  liquid  splashing  up  into 
the  condenser.  The  steam  delivery  tube  should  be  slightly  bent,  as 
shown.  Rubber  stoppers  should  not  be  used.  In  order  to  prevent 
excessive  condensation  of  steam  the  distilling  flask  should  be  directly 
heated,  and  a  soluble  salt  may 
be  added  to  raise  the  tempera- 
ture. The  distillate  may  consist 
of  a  solution  in  water  (acetic 
acid — see  p.  476),  or  of  two 
layers  (aniline — see  p.  351),  or  a 
solid  may  separate  (o-nitro- 
phenol — see  p.  272).  If  the 
last  tends  to  choke  the  condenser 
the  cooling  water  should  be 
turned  off  occasionally.  Steam 

may  be  substituted  by  alcohol  or  ether  vapour  in  particular  cases. 
Control  tests  should  be  made  occasionally  to  determine  the  completion 
of  the  distillation  ;  these  tests  may  be  physical  or  chemical,  depending 
on  the  nature  of  the  substance.  For  theoretical  discussion  see  "  Outlines 
of  Physical  Chemistry,"  Senter,  p.  90. 

Superheated  Steam. — This  is  used  for  distilling  substances  which  are 
difficultly  volatile.  The  steam  from  the  generator  is  passed  through  a 
copper  spiral  (Fig.  15)  which  is  heated  by  a  Bunsen  flame,  and  which  has 


Fig.  li 


24 


SYSTEMATIC  ORGANIC  CHEMISTRY 


a  side  tube  attached  for  a  thermometer.  This  tube  is  placed  on  the  exit 
tube,  and  as  far  away  as  possible  from  the  flame. 

Continuous  Steam  Distillation. — The  appa- 
ratus (Fig.  16)  is  very  convenient  when  this 
process  has  to  be  carried  on  for  some  time. 
The  substance  to  be  steam  distilled  is  placed 
in  the  round-bottomed  flask  A  along  with 
water  if  none  is  present.  To  the  flask  is 
attached  through  a  cork  a  tube  delivering  to 
a  vertical  tube  B,  and  with  a  small  side 
tube  C.  A  condenser  is  fitted  to  the  top  of 
the  vertical  tube  and  a  receiver  D  of  the 
type  shown,  or  a  flask  with  a  two-holed 
stopper.  The  small  side  tube  C  is  attached 
to  a  delivery  tube  E  fixed  to  the  receiver  by 
means  of  a  rubber  tube.  When  the  flask  is 
boiled  the  vapour  is  condensed  in  the  con- 
denser and  the  liquid  falls  into  the  receiver. 
When  this  process  has  been  continued  for 
some  time,  the  top  layer  of  water  in  the 
receiver  gradually  rises,  and  when  it  reaches 
the  level  of  the  small  side  tube  C  passes  back 
automatically  into  A.  The  process  is  now  con- 
tinuous. The  liquid  in  the  receiver  can  be 
separated  when  desired  by  opening  the  tap  on 
the  bottom  of  the  receiver. 
When  the  liquid  to  be  steam-distilled  is  lighter  than  water,  the  small 
glass  tube  E  is  extended  to  the  bottom  of  the  receiver. 


Fig.  16. 


Dry  Distillation. 

This  is  a  process  which  is  occasionally  used  in  the  laboratory  ;  it  is 
usual  to  perform  the  distillation  in  an  iron  or  copper  vessel  as  glass  will  not 
stand  the  heat.  In  order  to  prevent  a  cake  forming,  and  thus  secure 
uniform  heating,  it  is  advisable  to  mix  the  substance  to  be  distilled  with 
iron  turnings  which  conduct  the  heat  into  the  interior  of  the  mass,  pro- 
vided, of  course,  that  the  iron  turnings  have  no  chemical  action  on  the 
substance. 

Vacuum  Distillation. 

Some  liquids  decompose  when  distilled  in  the  ordinary  way  ;  these 
can  generally  be  distilled  under  reduced  pressure.  The  apparatus  used 
is  shown  in  the  sketch  (Fig.  17)  and  may  be  of  glass,  provided  large  vessels 
are  not  used.  It  is  usual  to  heat  the  distilling  flask  in  a  bath  and  not  by 
direct  heat.  The  distilling  flask,  which  may  be  of  the  ordinary  type  or, 
better,  having  two  necks  as  shown  (Fig.  18),  should  be  wrapped  in  asbestos 
cloth,  which  acts  as  a  protection  as  well  as  a  preventative  of  loss  of  heat  by 
radiation.  To  the  flask  is  attached  a  glass  tube  drawn  out  to  a  fine  capillary 


APPARATUS  AND  METHODS 


25 


which  dips  below  the  surface  of  the  liquid.  By  the  passage  of  small 
quantities  of  air,  or  some  other  gas  if  air  is  unsuitable,  regular  boiling  is 
maintained,  and  this  is  of  extreme  importance.  A.  rubber  tube  with  screw 


Fig.  17. 


clip  may  be  connected  to  the  top  of  the  capillary  tube  so  as  to  regulate  the 
air  supply.  Provided  the  liquid  has  no  action  on  rubber,  rubber  stoppers 
should  be  used  ;  they  should  be  smeared  with  vaseline  before  inserting. 
Good  corks,  however,  are  quite  satisfactory  if  covered  with  collodion  after 


Fig.  18.    (Claisen).  Fig.  19. 


insertion,  or  charred  as  described  on  p.  7.  Between  the  receiving  flask 
and  the  pump  is  placed  a  manometer  for  reading  the  pressure.  If  the 
ordinarv  water  pump  is  used  a  water  trap  (Fig.  19)  must  be  inserted 
between  the  pump  and  the  manometer  to  prevent  water  sucking  back  into 
the  apparatus.    When  the  distillation  is  to  be  discontinued  the  flame 


26 


SYSTEMATIC  ORGANIC  CHEMISTRY 


should  be  extinguished  and  air  allowed  to  enter  by  carefully  opening  the 
tap  attached  to  the  water  trap. 

Vacuum  distillation  may  be  used  in  fractionating  liquids.  The  apparatus 
is  similar  except  that  facilities  are  provided  in  the  receiving  vessel  for 
collecting  different  fractions.  Two  sketches  (Figs.  17,  20)  show  suitable 
types  of  receivers  for  use  in  fractionating  under  reduced  pressure.  The 
desiccator  type  is  shown  in  Fig.  17,  and  contains  six  or  seven  small 
receivers  into  which  the  distillate  Can  be  run,  different  fractions  being 
obtained  by  turning  the  handle  on  the  top,  thus  bringing  another  receiver 
into  position.   This  avoids  breaking  the  vacuum.   Fig.  20  shows  a  single 


4 


Fig.  20. 


receiver  which  can  be  emptied  without  breaking  the  vacuum.  While  a 
fraction  is  being  collected,  A  and  B  are  closed  while  C  is  open.  The  receiver 
is  emptied  by  closing  C  and  opening  A  and  B.  While  the  next  fraction  is 
being  collected  the  receiving  flask  may  be  removed. 

It  sometimes  happens  that  a  liquid  "  bumps  "  violently  even  with  the 
addition  of  a  few  porcelain  clips  and  the  passage  of  a  fine  gas  current 
through  the  flask.  The  best  plan  in  such  cases  is  to  immerse  the  flask  so 
far  into  the  heating  bath  (see  p.  35)  that  the  level  of  the  latter  is 
above  the  level  of  the  liquid  in  the  flask.  In  this  way  the  vapour  is  super- 
heated, and  bumping  does  not  occur. 

A  convenient  apparatus  for  distilling  liquids  of  high  boiling  point  under 
reduced  pressure  is  shown  in  Fig.  21,  in  which  the  receiver  is  an  ordinary 


APPARATUS  AND  METHODS 


27 


distilling  flask,  and  is  kept  cool  by  a  current  of  cold  water  (for  another 
type  of  receiver  see  Fig.  22). 

As  with  glass  flasks  there  is  a  risk  that  they  may  collapse  under  a 
vacuum,  especially  when  heated 
to  high  temperatures,  the  eyes 
should  be  protected  by  goggles 
when  using  them  as  above. 

Pumps. — The  lowest  pressure 
obtainable  by  a  water  pump  is 
the  vapour  pressure  of  water  at 
the  temperature  of  the  water 
(usually  10 — 15  mms.).  For 
pressures  below  this  a  mechani- 
cal pump  must  be  employed, 
which  in  some  cases  reduces  the 
pressure  to  less  than  1  mm. 

Note. — The  boiling  points  of 
high  boiling  point  liquids  are 
reduced  by  about  100°  at  10 — 
15  mms. 

A  Receiver  for  Distillation  in 
a  Current  of  Gas  or  under  Reduced  Pressure. — The  receiver  shown  in 
Fig.  22  can  be  used  to  fractionate  liquids  in  a  current  of  gas  or  under 

reduced  pressure. . 

The  condensing  liquid  is  first  collected 
in  A,  the  tap  B  being  turned  so  as  to 
connect  tubes  b  and  c.  The  gas  current 
meanwhile  passes  from  A  into  C  where  it 
displaces  air  and  prepares  C  for  the  recep- 
tion of  the  fraction.  The  tubes  d  and  e  are 
shown  as  for  a  heavy  gas,  e.g.,  C02  ;  for  a 
light  gas  the  relative  depths  to  which  they 
enter  the  flask  must  be  reversed. 

To  isolate  the  fraction,  B  is  turned  to 
put  c  in  communication  with  A.  The 
liquid,  helped  by  the  gas-current,  passes 
into  C,  B  is  turned  through  180°,  and  the 
tube  c  swept  out  by  gas  passing  from  b. 
Taps  D  and  E  are  closed,  and  the  ground- 
glass  joint  F  opened.  A  new  flask  is  put 
on  at  the  joint,  and  when  the  air  in  it  has 
been  swept  out,  the  next  fraction  can  be 
collected.  If  it  is  necessary  to  collect  the 
fractions  at  very  short  intervals,  several 
flasks  can  be  swept  out  simultaneously 
by  connecting  them  in  series  to  /.  If 
glass  joints  are  unnecessary  throughout,  pieces  of  rubber  tubing  can  be 
used  for  connecting  the  flasks  together. 


Fig.  22. 


28 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Fig.  23. 


As  shown,  the  apparatus  is  adapted  for  the  collection  of  very  readily 
oxidisable  liquids.  In  many  cases  it  will  not  be  necessary  to  have  taps 
D  and  E  ;  and  F  can  be  replaced  by  a  rubber  connection.  The  apparatus 
can  also  be  used  for  fractionation  in  vacuo.  The  vacuum  pump  is  con- 
nected at/,  and  while  a  fraction  is  collecting,  exhaustion  takes  place  from 
b  to  c.  The  fraction,  after  being  sucked  into  C  by  turning  B  through  180°, 
is  isolated  by  closing  B  by  a  right-angle  turn,  closing  E  and  disconnecting 
at  /.  Air  or  other  gas  can  then  be  admitted  through  E,  and  F  discon- 
nected. If  preferred,  E  can  conveniently  be  a  three-way  tap.  Another 
flask  is  then  fitted  on,  and  when  exhausted,  b  and  c  are  put  in  communica- 
tion. To  save  time,  several  flasks  can  be  kept  exhausted  by  attaching 
them  in  series  to/ and  to  the  pump  (J.  S.  C.  L,  41,  59  (T.)  ). 

Sublimation. 

Sublimation  is  a  process  used  for  the  purification  of  some  compounds, 
especially  when  the  quantity  of  substance  is  small.    The  first  point  to 

determine  is  that  the  substance  does  actually 
sublime.  This  is  done  by  heating  a  little  of 
the  substance  in  a  dry  test  tube  held  in  an 
almost  horizontal  position.  The  sublimate,  if 
any,  will  collect  on  the 
colder  parts  of  the  tube. 
Several  types  of  apparatus  are  available  for  sub- 
limation. If  the  substance  sublimes  readily,  the  fol- 
lowing apparatus  is  convenient.  It  consists  of  two 
watch-glasses  clamped  together  by  a  brass  clip,  the 
substance  being  placed  in  the  lower  glass  and  a  perfo- 
rated filter  paper  between  them.  The  sketch  (Fig.  23) 
shows  the  arrangement.  This  is  heated  on  a  sand 
bath.  The  sublimate  collects  in  the  upper  glass,  and 
the  filter  paper  prevents  the  sublimate  from  falling 

into  the  residue.  The  upper 
watch-glass  may  be  kept  cool 
by  covering  it  with  several 
pieces  of  damp  filter  paper 
and  wetting  these  from  time 
to  time.  The  upper  watch- 
glass  may  be  replaced  by  an  inverted  glass  filter 
funnel  with  a  plug  of  cotton  wool  in  its  stem 
(Fig.  24). 

When  the  substance  is  difficult  to  sublime,  it  may  be  heated  m  a  crucible 
placed  in  a  round  hole  in  a  piece  of  asbestos  board.  The  crucible  is  covered 
with  a  large  clock-glass  and  a  small  flame  is  used  so  that  the  heat  is  directed 
only  on  to  the  crucible,  as  shown  in  Fig.  25. 

Filtration  (see  also  p.  9). 
Filtration  by  means  of  suction  is  generally  employed  where  possible  in 
the  operations  of  organic  chemistry,  since  more  rapid  and  more  complete 


Fig.  24. 


Fig.  25. 


APPARATUS  AND  METHODS 


21) 


separation  of  the  mother  liquor  is  in  this  way  effected.  For  this  purpose 
several  types  of  apparatus  are  in  use.  For  large  quantities  of  material  the 
Buchner  funnel  and  flask  (Fig.  26)  is  used,  the  filter  paper  being  cut  so  as 
to  cover  the  perforations.  If  filter  paper  is  attacked  by  the  liquor,  cloth, 
such  as  flannel  or  cotton,  might  be  used  instead. 
For  highly  corrosive  liquids,  a  layer  of  fibrous 
asbestos  should  be  employed  as  filtering 
medium  ;  this  is  prepared  by  boiling  asbestos 
wool  with  hydrochloric  acid,  then  pouring  on 
to  the  Buchner  funnel  and  washing  thoroughly 
with  water  while  suction  is  applied.  If  neces- 
sary, the  asbestos  is  then  dried  by  washing 
successively  with  alcohol  and  ether.  In  al] 
cases  the  filtering  medium  should  be  moistened 
with  the  solvent  used,  and  well  pressed  down  on 
the  perforated  plate. 

An  ordinary  funnel  in  which  is  placed  a  perforated  disc  (Fig.  27a)  may 
be  used  instead  of  the  Buchner  funnel,  and  this  form  is  very  convenient 
for  separating  small  quantities  of  solids.  The  paper  should  be  cut  slightly 
larger  than  the  disc,  and  should  be  carefully  placed  in  position,  and  pressed 
down  after  moistening. 

For  separating  small  quantities  of  liquid  the  apparatus  (Fig.  27b)  is  very 


Fig.  27. 


suitable  ;  the  liquid  is  received  in  a  test  tube  placed  inside  the  Buchner 
flask. 

The  apparatus  (Fig.  28)  shows  the  most  convenient  arrangement  when 
the  filtrate  is  further  required.  It  consists  of  a  bell  jar  cemented  with  vase- 
line to  a  ground-glass  plate  ;  the  double-holed  rubber  stopper  carries  the 
filter  funnel  and  a  tube  for  connecting  to  pump.  The  liquid  is  collected  in  a 
receiver  placed  inside  the  bell  jar.  The  great  advantage  of  the  apparatus 
is  that  any  type  of  receiver  may  be  employed.  If  the  filter  funnel  has  a 
long  stem,  it  may  be  used  in  conjunction  with  a  hot-water  jacket  (Fig.  3) 
or  an  ice  jacket  (Fig.  4). 


30  SYSTEMATIC  ORGANIC  CHEMISTRY 

In  order  to  separate  as  much  liquid  as  possible  from  a  large  bulk  of 
solid,  the  solid,  after  being  filtered  in  the  ordinary  way  by  means  of  a 
Buchner  funnel  and  well  pressed,  is  removed  from  the  funnel,  placed  in  a 

stout  piece  of  cloth  and  tightly 
wrapped.  It  is  then  placed  in  a 
press  of  the  ledger  type  and  pressure 
gradually  applied  (of.  Drying). 


Decolorisation. 

It  often  happens  that  the  com- 
pound prepared  in  a  particular  pre- 
paration is  discoloured ;  various 
methods  are  used  to  remove  traces  of 
colouring  and  of  tarry  matter.  The 
most  common  is  to  boil  up  the  sub- 
stance in  solution  with  animal  char- 
coal— added  in  the  cold — and  then 
to  filter  and  recover  the  compound 
from  the  filtrate  by  crystallisation 
or  distillation.  Very  little  of  good 
Fig.  28.  decolorising  carbon  is  necessary  as  a 

rule,  and  that  may  be  re-vivified  by 
impregnating  with  a  concentrated  zinc  chloride  solution,  igniting,  and 
washing  with  acid.  It  should  be  remembered  that  animal  charcoal 
contains  only  about  10%  of  carbon,  the  remainder  being  phosphates 
of  different  metals,  iron,  etc.  ;  this  should  be  considered  especially 
when  decolorising  in  acid  solution.  If  any  of  these  substances  are 
likely  to  be  harmful,  the  animal  charcoal  should  be  boiled  up  with 
.hydrochloric  acid,  filtered,  washed  and  dried.  Sometimes  a  solution 
remains  cloudy  after  filtration.  As  a  rule  this  cloudiness  can  be 
removed  by  adding  very  small  equivalent  quantities  in  solution  of 
calcium  chloride  and  sodium  phosphate.  The  calcium  phosphate  pre- 
cipitated usually  brings  down  all  gelatinous  matter  and  may  then  be 
removed  by  filtration. 

Decoloration  is  sometimes  due  to  oxidation,  and  the  colouring  matter 
may  often  be  removed  by  passing  S02  gas  through  the  solution,  always 
provided  that  this  has  no  action  on  the  substance  in  solution. 

Salting  Out. 

Some  substances  which  are  soluble  in  water  are  not  soluble  or  only 
slightly  soluble  in  solutions  of  certain  salts,  such  as  sodium  chloride, 
calcium  chloride,  sodium  acetate,  sodium  sulphate.  The  salt  may  be 
added  in  the  solid  form  or  as  a  saturated  solution.  By  this  means 
alcohol  and  acetone  can  be  separated  from  their  solutions  in  water. 

The  process  is  used  very  largely  on  the  technical  scale  for  the  separation 
of  dyestufis  (see  pp.  373,  374). 


APPAKATUS  AND  METHODS 


3] 


Extraction  of  Solids. 

When  it  is  required  to  separate  a  solid  from  an  impurity,  it  is  desirable 
to  carry  out  the  extraction  in  a  Soxhlet  apparatus,  a  sketch  of  which  is 
shown  (Fig.  29).     The  substance  to  be  extracted  is  placed  in  a  paper 
thimble  A  which  is  set  in  position  in  the  main 
Soxhlet  tube,  a  loose  plug  of  cotton  wool  being 
placed  in  the  top  of  the  thimble.    The  Soxhlet  is 
attached  to  a  flask  which  contains  a  small  amount 
of  a  solvent;  the  solvent  chosen  should  be  such 
that  either  the  desired  substance  or  the  impurity 
is  insoluble,  or  nearly  so.    A  condenser  is  attached 
to  the  Soxhlet  tube  ;  the  ball  condenser  C  shown 
in  sketch  is  the  most  convenient. 

When  the  solvent  is  boiled,  the  vapour  passes 
through  side  tube  D  to  the  condenser,  from  which 
liquid  drops  back  to  the  thimble.  When  this  liquid 
reaches  the  top  of  the  side  tube  E,  it  automatically 
syphons  back  into  the  flask  B  with  the  extracted 
matter  in  solution.    The  process  is  continuous. 

It  is  advisable  to  use  a  minimum  quantity  of 
solvent  at  the  beginning  and,  if  necessary,  to  add 
more  solvent  through  the  condenser.  More  rapid 
extraction  can  be  brought 
about  if  the  substance  is  inti- 
mately mixed  with  some  inert 
substance,  such  as  glass  or 
sand. 

When  the  extraction  is 
judged  to  be  complete,  the 
Soxhlet  is  removed  and  the 
substance  crystallised  from  the 
solution  remaining  in  the  flask. 


Separation  of  two  Immiscible 
Liquids. 


Fig.  29. 


For  this  purpose,  funnels  of  the  types  Fig.  30  are 
used.  The  liquids  to  be  separated  are  run  into  the 
funnel,  and  after  standing  for  some  time,  the  stopper 
at  the  top  is  removed  and  the  more  dense  liquid  is  run 
off  through  the  tap  at  the  bottom.  If  the  upper 
layer  is  required,  it  is  poured  out  through  the  top  of 
the  funnel  after  running  off  the  bottom  layer ;  this  is 
to  prevent  contamination  with  the  liquid  in  the  stem  ■ 
and  tap  of  the  funnel.  In  all  cases  a  funnel  of  convenient  size  should  be 
chosen. 

If  the  volume  of  liquids  is  small,  separation  can  be  effected  by  the  use 
of  a  small  pipette  to  which  Is  attached  a  length  of  rubber  tubing  ;  the 


Fig.  30. 


32  SYSTEMATIC  ORGANIC  CHEMISTRY 

rubber  tubing  is  held  in  the  mouth,  gentle  suction  is  applied,  and  the  eye 
kept  on  a  level  with  the  common  surface  of  the  liquids. 

Separation  by  Extraction. — Separating  funnels  are  again  used  for  this 
purpose.  The  substance  to  be  extracted  is  generally  in  solution  or  sus- 
pension in  water.  A  solvent  which  is  immiscible  with  water  and  in  which  j 
the  substance  is  soluble  is  added— in  small  quantities  at  first.  The  funnel 
is  stoppered  and  agitated,  holding  the  tap  and  stopper  closed,  after  which 
it  is  set  aside  in  a  vertical  position  until  the  liquids  separate.  Separation 
is  then  effected  as  above.  The  solvent  most  commonly  employed  is  ether, 
but  benzene,  chloroform,  ligroin  and  amyl  alcohol  are  used  in  special 
circumstances. 

In  all  cases  extraction  should  be  carried  out  more  than  once,  the  extracts  1 
being  added  together.    The  amount  of  substance  which  goes  into  solution 
in  ether,  etc.,  depends  on  the  distribution  coefficient,  that  is,  the  ratio  of 
the  concentrations  in  the  two  solvents  after  equilibrium  is  attained.  This 
ratio  is  constant  for  any  given  temperature,  provided 
the  molecular  weight  of  the  solute  does  not  vary  in 
either  solvent  (see  "  Outlines  of  Physical  Chemistry," 
Senter,  p.  177).    It  follows  then  that  extraction  may 
have  to  be  repeated  several  times,  and  also  that  it  is 
more  efficient  to  extract  a  number  of  times  with  suc- 
cessive small  quantities  of  solvent  rather  than  once 
with  a  large  quantity. 

When  a  quantity  of  the  substance  separates  from  the 
solution  as  an  oil,  this  oil  should  be  separated  before 
extraction  is  attempted. 

In  extraction  with  ether  the  following  points  should 
be  noticed  : — 

1.  All  burners  in  the  immediate  vicinity  should  be 
extinguished. 

2.  After  shaking,  the  funnel  should  be  inverted  and 
the  pressure  released  by  gradually  opening  the  stopcock. 

3.  If  an  emulsion  persists  after  standing,  this  may  frequently  be" 
destroyed  by  agitating  the  ethereal  layer  with  a  glass  rod.  Addition  of  a 
few  drops  of  alcohol  is  sometimes  effective.  In  special  cases  filtration 
may  be  useful.  If  the  funnel  be  held  in  a  stream  of  warm  water  for  a 
time,  separation  may  be  facilitated. 

4.  Extraction  is  complete  when  a  sample  of  the  ether  layer  when 
evaporated  to  dryness  leaves  no  residue. 

5.  Ether  is  soluble  in  water  to  the  extent  of  8%.  If  the  aqueous 
volume  to  be  extracted  is  large,  it  should  be  saturated  with  common  salt, 
in  which  solution  ether  is  much  less  soluble. 

6.  Water  is  soluble  in  ether  to  the  extent  of  1-5%.  It  follows,  therefore, 
that  the  ether  extract  must  be  dried  (see  p.  34)  before  removing  the  ethei 
by  evaporation. 

7.  The  ether  is  generally  removed  by  distillation.  A  moderate  sized 
flask  should  be  used  and  more  solution  added  from  time  to  time.  The 
apparatus  shown  in  Fig.  31  enables  the  additions  to  be  made  without 


APPAKATUS  AND  METHODS 


33 


interruption  of  the  distillation.  The  flask  is  fitted  with  a  two-holed 
stopper  carrying  a  dropping-funnel  and  a  glass  tube.  By  means  of  a  piece 
of  rubber  tubing  and  a  second  short  piece  of  glass  tubing  inserted  through 
a  cork,  the  top  of  the  funnel  is  connected  through  the  first  piece  of  glass 
tubing  with  the  interior  of  the  flask  ;  the  rubber  tubing  on  this  connection 
carries  a  spring  clip.  The  ethereal  solution — a  portion  at  a  time — is  placed 
in  the  funnel  and  the  cork  inserted  in  the  neck  of  the  funnel.  The  stop- 
cock of  the  funnel  and  the  spring  clip  are  then  opened  simultaneously,  and 
the  ether  flows  into  the  flask  without  interruption,  since  the  pressure 
above  the  ether  in  the  funnel  and  the  pressure  inside  the  flask  have  been 
equalised  by  the  opening  of  the  spring  clip.  When  the  ether  has  run  in, 
the  tap  and  the  clip  are  closed. 

8.  Salts  are  generally  insoluble  in  ether.  Ferric  chloride,  mercuric 
chloride,  mercuric  iodide,  stannous  chloride  and  chromic  anhydride, 
however,  are  fairly  soluble. 

Drying. 

Drying  of  Solids.— (a)  At  Ordinary  Temperature. — When  the  solid  is 
insoluble  in  a  volatile  solvent,  such  as  ether  or  petroleum  ether  (40° — 60°), 
and  this  solvent  is  miscible  with  the  solvent 
from  which  the  solid  was  crystallised,  drying 
may  be  greatly  facilitated  by  washing  the 
substance  while  still  on  the  filter  with  such 
a  volatile  solvent.  The  usual  method  of 
drying  at  ordinary  temperature  consists  in 
spreading  the  solid  on  several  layers  of  filter 
paper  or  on  a  porous  plate,  and  leaving 
until  dry.  It  is  necessary,  however,  to  pro- 
tect the  solid  from  dust  contamination  by 
covering  with  filter  paper  or  watch-glass  in 
such  a  manner  that  free  access  of  air  is  per- 
mitted. The  drying  may  be  more  quickly 
carried  out  by  placing  the  solid  on  a  porous 
tile  in  a  vacuum  desiccator. 

Desiccators. — These  are  of  two  types,  the 
ordinary  and  the  vacuum  (see  Fig.  32). 
The  drying  in  the  latter  is  generally  6 — 7 
times  quicker  than  in  the  former.    The  Fig.  32. 

desiccator  is  charged,  according   to  the 

nature  of  the  substance  to  be  absorbed,  with  one  or  other  of  the  following 
substances — 

Cone.  H2S04  :  to  absorb  water,  basic  substances. 

Granular  calcium  chloride  :  to  absorb  water,  alcohols,  some  basic 
substances. 

Solid  sodium  or  potassium  hydroxide  :  to  absorb  water,  acids,  phenols, 

alcohols,  esters. 
Quicklime  :  to  absorb  water,  acids. 

S.O.C.  D 


SYSTEMATIC  OKGANIC  CHEMISTKY 


Soda  lime  :  to  absorb  water,  acids. 

Paraffin  wax  :  to  absorb  carbon  disulphide,  ether,  chloroform,  benzene. 
It  is  obvious  from  the  foregoing  list  that  impurities  as  well  as  solvent 
may  be  removed  from  a  solution  by  exposure  in  a  desiccator  containing  a 
suitable  absorbent.  It  is  essential  that  the  absorbent  does  not  react  with 
the  substance  to  be  dried.  Of  drying  agents,  cone.  H2S04,  P205  and 
solid  KOH  are  equal  in  drying  power  and  most  effective  for  ordinary 
purposes.  Solid  NaOH  and  CaCl2  are  likewise  nearly  equivalent  in  drying 
power. 

N.B. — A  suction  flask  should  always  be  inserted  between  a  vacuum 
desiccator  and  a  water  pump  when  the  latter  is  used,  as  slight  varia- 
tions in  water  pressure  may  result  in  water  being  sucked  back  into  the 
desiccator. 

(b)  At  Higher  Temperature. — If  it  is  desired  to  dry  a  solid  at  a  tempera- 
ture higher  than  ordinary,  a  test  should  first  be  made  with  a  small  portion. 
This  is  necessary  since  many  substances  decompose  at  relatively  low 
temperatures  and  such  temperatures  should  be  noted.  Moreover,  the 
presence  of  slight  impurities  or  of  solvent  may  considerably  lower  the 
melting  point  of  the  solid.  Other  changes — decomposition,  loss  of  solvent 
of  crystallisation,  etc. — may  take  place  on  heating,  and  these  should  be 
noted. 

For  drying  at  temperatures  up  to  100°,  the  water  bath  or  steam  oven  is 
generally  used.  For  drying  at  higher  temperatures  the  air  oven  is  em- 
ployed, but  here  a  thermometer  should  be  inserted  and  particular  care 
taken  that  the  substance  is  not  over-heated.  A  very  convenient  form  of 
drying  apparatus  is  the  toluene  bath  (p.  35). 

Drying  of  Liquids. — (a)  At  Ordinary  Temperature. — Liquids  are  usually 
dried  by  the  addition  of  some  solid  dehydrating  agent,  such  as  granular 
calcium  chloride,  solid  caustic  potash  or  soda,  anhydrous  sodium  sulphate, 
anhydrous  potassium  carbonate,  anhydrous  cupric  sulphate,  phosphorus 
pentoxide,  metallic  sodium.  It  is  essential  that  the  drying  agent  should 
have  no  action  on  the  liquid  to  be  dried,  or  any  substance  dissolved  in  it, 
and  great  care  should  be  exercised  in  the  choice  of  a  drying  agent.  For 
example,  calcium  chloride  should  not  be  used  for  drying  alcohols  or 
amines.  Caustic  potash  or  soda  should  not  be  employed  for  drying 
acids,  phenols,  esters,  certain  halides,  etc.  The  minimum  quantity 
of  drying  agent  should  be  used,  otherwise  liquid  is  lost  by  absorption. 
After  standing  some  time,  the  liquid  is  separated  by  decantation  or 
filtration. 

The  drying  of  ethereal  solutions  is  an  operation  frequently  met  with  in 
the  laboratory,  for  in  most  cases  it  is  advisable  to  dry  an  ethereal  extract 
before  evaporating  off  the  ether.  Again,  to  dry  a  moist  solid,  it  is  often 
convenient  to  dissolve  it  in  ether  and  to  dry  the  ethereal  solution  with  a 
dehydrating  agent.  The  dry  solid  is  then  obtained  on  evaporation  of  the 
ether. 

(b)  At  Higher  Temperatures. — This  method  is  seldom  employed,  and  is 
only  effective  when  the  liquid  has  a  high  boiling  point  and  is  not  volatile 
in  steam. 


APPARATUS  AND  METHODS 


35 


Baths. 

Baths  are  used  for  heating,  drying,  etc.  ;  the  heating  can  be  thus  carried 
out  more  uniformly  than  is  possible  with  a  direct  name.    A  judicious 
selection  of  the  type  of  bath  required  for  any  operation  should  be  made — 
an  air  bath  should  not  be  used  if  a  water 
bath  suits  the  purpose.    In  all  cases  a 
means  of  ascertaining  the  temperature 
should  be  provided,  either  by  taking  the 
temperature  of  the  bath,  or  of  the  sub- 
stance heated  on  the  bath. 

Water  Bath.  —  This  is  employed  for 
heating  or  drying  up  to  100°.  For  tem- 
peratures below  100°  the  vessel  should  be 
immersed  in  the  water ;  for  100°  the 
vessel  should  be  so  far  immersed  as  to  be  largely  surrounded  by  steam. 
When  a  water  bath  is  to  be  used  for  many  hours  or  days,  a  constant-level 
arrangement  should  be  attached  (Fig.  33). 

Salt  Solutions.— Temperatures  above  100°  can  be  attained  by  the 
addition  of  salts  to  the  water.  The  boiling  points  of  a  few  saturated 
solutions  is  appended  : 


Fig.  33. 


Sodium  chloride 
Magnesium  sulphate 
Potassium  nitrate  . 
Sodium  nitrate 
Calcium  chloride  . 


B.P. 

109° 
108° 
116° 
121° 
180° 


Toluene  Bath  (Fig.  34), — This  bath  consists  of  a  double-walled  enclosure 
access  to  which  is  obtained  by  a  hinged  door  carrying  a  stout  rubber  joint. 
The  door  is  fastened  by 
thumb-screws.  Any  suit- 
able liquid  can  be  placed 
in  the  outer  jacket  to 
which  is  attached  a  con- 
denser ;  the  liquid,  how- 
ever, most  generally  used 
is  toluene  (B.P.  110°). 
The  inner  compartment 
is  fitted  with  an  exit  tube 


carrying  a  vacuum  gauge, 
and  this  may  be  attached 
to  a  vacuum  pump.  This 
offers  a  very  convenient 
method  of  drying  sub- 
stances at  a  temperature  — 
slightly  above  100°  and 
under  reduced  pressure. 

Air  Bath. — A  convenient  form  of  air  bath  is  made  of  sheet  iron,  and 


Fig.  34. 


36 


SYSTEMATIC  ORGANIC  CHEMISTRY 


completely  lined  on  the  outside  with  asbestos.  Air  ovens  are  generally 
used  for  temperatures  above  100°.  In  no  case  should  the  substance  be 
placed  on  the  lower  shelf  ;  the  bulb  of  the  thermometer  should  reach  close 
to  the  shelf  on  which  the  substance  is  placed. 

Sand  Bath— This  form  of  bath  is  used  for  temperatures  well  above  100°. 
A  thermometer  should  always  be  placed  in  the  substance  being  heated. 
It  is  important  that  the  layer  of  sand  should  only  be  just  thick  enough  to 
protect  the  vessel  from  excessive  heat. 

Oil  Bath— Suitable  oils  may  be  used  such  as  higher  boiling  paraffins, 
melted  paraffin  wax,  glycerine,  etc.  The  oil  should  not  be  heated  to  its 
flash  point,  and  the  surface  of  oil  exposed  should  be  as  small  as  possible. 


Fig.  35. 


Metal  Bath.— This  type  of  bath  is  the  most  suitable  for  heating  to  high 
temperatures.  Before  heating,  the  vessel  to  be  heated  should  be  held  in 
a  luminous  flame  until  covered  with  a  deposit  of  carbon  which  prevents  the 
fused  metal  from  adhering  to  the  flask  ;  it  also  renders  the  vessel  less 
liable  to  crack. 

The  following  metals  and  alloys  may  be  used  : — 

M.P. 

Bi  (4),  Cd  (1),  Pb  (2),  Sn  (1)  ....  65° 
Bi  (4),  Cd  (2),  Pb  (1),  Sn  (2)    ....  80° 

Bi  (3),  Pb  (2),  Sn  (2)  95° 

Bi(l),Pb(l),Sn(l)  .  .  .  .  .  122° 
Sn  .     MM     •        •  232° 

Pb  .  .  .  .  .  •  •  327° 
Zn       ,   .       •       •       •  419° 


APPARATUS  AND  METHODS 


37 


Mechanical  Agitation. 

The  importance  of  mechanical  agitation  cannot  be  over-estimated. 
In  some  preparations  a  yield  cannot  be  obtained  at  all  unless  efficient 
agitation  is  provided ; 
mechanical  agitation 
should  be  used,  there- 
fore, wherever  continuous 
agitation  is  essential.  A 
suitable  vessel  should 
first  be  chosen,  and  an 
agitator  made,  usually  of 
glass  rod,  to  suit  this  par- 
ticular vessel.  The  rela- 
tive densities  of  the  sub- 
stances to  be  mixed  must 
be  borne  in  mind  ;  obvi- 
ously it  will  require  much 
more  vigorous  agitation 
to  sulphonate  benzene,  or 
to  reduce  nitrobenzene 
with,  say,  iron,  than  to 
fuse  a  sulphonic  acid 
with  caustic  soda,  or  to 
reduce  dinitrobenzene 
with  sodium  sulphide 
solution  —  due  to  the 
much  greater  differences 
in  the  specific  gravities  of 
the  reacting  substances. 
The  propeller  type  of  agi- 
tator  is  always  service- 
able provided  the  speed  is  high.    The  driving  force  may  be  electric  or 

hydraulic,  but  various  simple  devices 
can  be  adopted  depending  on  the 
nature  of  the  chemical  reaction.  For 
example,  air  or  other  gas  may  be 
passed  into  the  mixture,  etc. 

Where  active  boiling  is  taking  place 
in  a  mixture,  mechanical  agitation  is 
usually  unnecessary. 

The  sketch  (Fig.  35)  shows  a  battery 
of  agitators  driven  by  an  electric 
motor  and  employing  different  types 
of  agitators.  By  changing  the  driving 
belt  to  different  pairs  of  pulleys, 
different  speeds  of  agitator  can  be 
obtained.  It  is  always  wise  to  have 
some  idea  of  the  speed  of  agitation. 


Fig.  37. 


86395 


38 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Sulphonation  Pot. — The  most  satisfactory  method,  however,  of  using 
mechanical  agitation  is  in  conjunction  with  a  specially  constructed  piece 
of  apparatus.  Various  types  can  now  be  procured  and  some  are  very 
effective.  Fig.  36  shows  one  such.  It  consists  of  a  cast-iron  pot  with  a 
lid  carrying  the  brass  bearing  and  gear  wheels  of  the  central  shafts.  The 
large  driving  pulley  drives  the  outer  shaft  in  one  direction  and  the  inner 
shaft  in  the  opposite  direction,  a  suitable  form  of  iC  blade  "  being  attached 
to  each.  The  lid  is  attached  to  the  pot  by  thumb -screws,  suitable  jointing 
matter  being  used,  such  as  rubber.  Openings  are  provided  in  the  lid  for 
reflux  condenser,  thermometer,  and  addition  tube.  The  apparatus,  which 
may  be  driven  from  an  electric  motor,  is  admirably  suited  for  sulphona- 
tions,  nitrations,  and  reductions.  When  such  an  apparatus  cannot  be 
obtained  the  apparatus  (Fig.  37)  in  glass  is  recommended. 

Heating  under  Pressure. 

When  a  mixture  of  substances  is  heated  in  an  enclosed  space  no  volatile 
matter  can  escape,  and  hence,  at  a  certain  period  in  the  heating,  pressure 
begins  to  develop.  Substances  or  solutions  may  thus  be  heated  to  a 
temperature  above  the  boiling  point  of  any  or  all  of  them  without  incur- 
ring  the  loss  of  reacting  substances  or  reaction  products  ;  and  the  method 
has  the  advantage  that  many  reactions  which  cannot  be  brought  about 
by  boiling  substances  in  open  vessels  can  be  easily  brought  about  by 
heating  under  pressures  above  atmospheric.  If  it  is  desired  to  heat 
two  substances  under  pressure,  but  not  to  a  temperature  above  the  I 
boiling  point  of  either,  a  third  substance  of  lower  boiling  point  which  has  I 
no  chemical  action  on  either  of  them  is  introduced. 

Heating  under  pressure  is  generally  done  in — (a)  Sealed  Tubes,  or  (6) 
Autoclaves. 

(a)  Sealed  Tubes. — As  only  small  quantities  of  substance  can  be  dealt 
with,  the  method  is  only  applicable  for  small  scale  experiments  or  quantita- 
tive work  {e.g.,  Estimation  of  Halogens — Carius).  Generally  soft  glass  tubes  j 
about  50  cms.  long,  18 — 20  mms.  outside  diameter,  and  walls  2-5 — 3  mms. 
thick,  are  used,  but  if  the  contents  attack  soft  glass,  or  if  large  quantities 
of  gas  are  evolved  on  heating,  or  if  the  temperature  of  heating  is  high, 
tubes  of  difficultly  fusible  potash  glass  should  be  employed,  since  these 
are  more  resistant  to  chemical  action  and  do  not  crack  so  readily. 
As  glass  deteriorates  with  age,  a  piece  of  new  glass  should  be  selected  for 
sealed  tube  work.  A  suitable  length  is  cut  (see  p.  440),  thoroughly  washed, 
and  after  being  allowed  to  drain  for  some  time  is  dried  by  warming  with  a  4 
moving  flame  while  a  current  of  air  is  blown  through  it. 

To  seal  one  end  of  the  tube,  about  two  inches  of  the  tube  at  this  end  is 
heated  by  revolving  it  in  the  smoky  flame  of  a  blowpipe  for  a  few  minutes. 
The  blast  is  then  turned  on  slowly,  and  the  tube,  while  held  in  one  hand  j 
at  an  angle  of  45°,  heated  at  the  end  until  softening  takes  place,  when  a 
previously  warmed  glass  rod  held  in  the  other  hand  is  fused  on  to  it.  The  ; 
blast  flame  is  adjusted  so  that  it  will  heat  a  zone  of  glass  about  as  broad  as 
the  diameter  of  the  tube  to  be  sealed,  and  is  directed  at  a  point  about  3  cms.  j 


APPARATUS  AND  METHODS 


39 


from  the  end  of  the  tube,  which  is  slowly  brought  into  the  flame  with 
constant  rotation.  When  the  glass  begins  to  thicken  the  ends  are  slowly 
pulled  asunder,  taking  care  not  to  pull  out  the  softened  glass  too  much, 
but  to  allow  the  sides  to  fall  together,  as  shown  at  A  (Fig.  38).  When 
this  occurs,  the  narrow  part  is  heated  till  it  melts  and  the  ends  pulled 
asunder.  The  closed  end  should  present  the  appearance  shown  at  D 
If  a  considerable  mass  of  glass  be  left  at  d,  it  may  be  removed  by 
heating  it  to  redness,  touching  it  with  the  pointed  end  of  a  cold  glass 
tube,  to  which  it  will  adhere,  and  by  which  it  may  be  pulled  away.  Any 
blob  of  glass  remaining  is  heated  in  a  small  blowpipe  flame,  and  by  gently 
blowing  with  the  mouth  into  the  open  end  of  the  tube,  and  re-heating  and 
blowing  again,  the  blob  can  be  removed,  and  finally,  by  using  a  rather 
larger  flame,  heating  and  blowing  alternately,  the  end  is  neatly  rounded — 


1      \  H 


1  P  E  1  >=— a 

Fig.  38. 

shown  at  E.  After  cooling  slightly  the  hot  end  of  the  tube  is  annealed 
by  holding  it  for  a  few  minutes  in  a  luminous  flame. 

Hard  glass  is  much  more  easily  worked  in  the  oxygen- coal  gas  flame, 
obtained  by  attaching  a  cylinder  of  oxygen  in  place  of  the  air  blast  to  the 
lamp. 

Filling  the  Tube. — Since  the  tube  is  afterwards  sealed  at  the  open  end, 
it  is  necessary  when  filling  the  tube  to  take  care  that  none  of  the  ingredients 
come  into  contact  with  it  near  that  end.  The  tube  should  be  clamped  in 
a  vertical  position  beside  the  working  bench,  and  a  funnel  tube,  having  a 
stem  as  wide  as  the  tube  will  admit,  is  inserted  in  the  open  end  ;  through 
this  the  substances  are  added.  In  analytical  work  (see  Estimation  of 
Halogens)  the  weighed  substance  should  be  introduced  in  a  container  of 
its  own.  When  fuming  liquids  are  employed  (see  Preparation  of  Para- 
nitrobenzyl  Bromide)  these  should  be  placed  in  test  tubes  stoppered  with 
glass  wool  or  asbestos  ;  obnoxious  fumes  during  the  sealing  process  are 
thus  largely  avoided.  When  withdrawing  the  funnel  tube,  care  is  taken 
to  avoid  bringing  it  into  contact  with  the  walls  of  the  tube.  The  amount 
of  substance  which  may  be  introduced  depends  on  the  conditions  ;  the 
tube  should  never  be  more  than  half  filled,  and  if  much  gaseous  products 


40 


SYSTEMATIC  ORGANIC  CHEMISTRY 


is  formed,  or  if  the  temperature  of  heating  be  high,  a  lesser  quantity 
should  be  introduced. 

Sealing. — The  tube  is  held  at  an  angle  of  45°,  and  in  a  manner  already 
described ;  the  open  end  is  warmed  in  a  smoky  flame,  then  heated  to 
softening,  and  a  glass  rod  sealed  on  to  it.  Likewise,  as  described  before, 
the  tube  is  heated  at  a  point  about  3  cms.  from  the  end  by  rotating  it  in  a 
blast  flame.  The  glass  is  evenly  heated  and  not  drawn  out,  but  when  the 
apparent  inside  diameter  of  the  tube  is  reduced  to  about  3  mms.,  the  tube 
is  quickly  withdrawn  from  the  flame  and  a  capillary  formed  by  slowly 
drawing  out  the  thickened  part  (Fig.  38).  In  order  to  secure  a  thick 
end  to  the  point  of  the  capillary  a,  about  2  cms.  of  the  tube  at  the 
shoulder  is  warmed  a  little  at  the  moment  of  finally  sealing  it ;  the  con- 
traction of  the  air  in  the  tube,  in  consequence  of  its  cooling,  ensures  the 


Sealing  of  Hard  Glass.— For  this  a  slightly  different  method  of  sealing  is 
employed.  As  soon  as  the  glass  is  sufficiently  soft,  it  is  not  thickened,  but 
is  drawn  out  at  once  to  a  wide  capillary.  By  directing  the  flame  on  the 
shoulder  of  the  tube  and  continuing  to  draw  out,  the  capillary  is  then 
lengthened  to  about  3  cms.  It  is  then  thickened  by  revolving  in  the 
flame  and  finally  sealed  off.  The  sealing  of  hard  glass'  requires  at  least  a 
first-class  blowpipe  ;  and  the  sealing  may  be  facilitated  by  placing  a  brick 
or  tile  near  the  flame  in  such  a  position  that  the  heat  is  reflected  on  to  the 
tube. 

As  soon  as  the  tube  is  sealed  and  annealed,  it  is  clamped  in  a  vertical 
position,  with  capillary  uppermost,  and  left  to  cool. 

Tube  Furnace  or  Bomb  Furnace- Heating. — When  cold,  the  tube  is  trans- 
ferred to  the  removable  metallic  cylinder  of  the  tube  furnace  (Fig.  39). 
The  cap  of  the  cylinder  is  screwed  on  and  the  latter  placed  in  position  in 
the  furnace.  Various  forms  of  furnace  are  used  :  the  common  forms  are 
heated  by  a  series  of  pinhole  gas-jets,  and  are  easily  regulated.  The 


Fig.  39. 


glass  at  a  running 
together  to  a  solid 
end  when  it  is 
melted  in  the 
fl  a  m  e.  If  it  is 
desired  to  collect 
a  gas  produced 
during  the  chemi- 
cal reaction,  the 
capillary  is  made 
several  inches 
long,  and  is  bent 
into  the  form  of  a 
delivery  tube.  It 
is  then  possible  to 
break  the  tip  of 
this  under  a  cylin- 
der in  a  trough  of 
liquid. 


APPARATUS  AND  METHODS 


41 


removable  cylinder  is  not  supplied  with  all  furnaces,  but  it  is  advisable  to 
have  it  for  the  following  reasons  :  (a)  The  furnace  may  be  approached 
without  fear  of  glass  splinters,  and  (b)  in  case  the  tube  bursts,  the  glass 
fragments  and  contents  (of  the  sealed  tube)  remaining  in  the  cylinder  can 
be  easily  removed. 

When  a  removable  cylinder  with  screw  cap  is  not  available,  the  sealed 
tube  is  placed  in  the  fixed  cylinder  of  the  furnace,  the  capillary  end 
pointing  towards  a  wall  of  the  furnace  room  so  that  no  damage  will  accrue 
in  case  of  an  explosion. 

At  the  commencement  of  the  heating,  small  flames  are  used  and  the 
temperature  raised  gradually  to  the  desired  point.  The  temperature  is 
indicated  by  a  thermometer,  inserted  through  a  cork  in  the  opening  at  the 
top  of  the  furnace,  the  bulb  of  the  thermometer  being  about  1  cm,  from 
the  bottom  of  the  iron  tube.  The  danger  of  the  bursting  of  sealed  tubes 
may  be  diminished  in  many  cases  by  interrupting  the  heating  after  a 
certain  length  of  time,  opening  the  capillary  after  the  tube  has  completely 
cooled,  and  allowing  the  generated  gases  to  escape.  The  tube  is  then 
resealed  and  heated  again.  Or,  to  take  an  example  of  bromination,  one 
half  the  necessary  quantity  of  bromine  may  be  added  at  first,  the  tube 
sealed  and  heated  to  the  desired  temperature  ;  the  tube  is  then  allowed  to 
cool,  after  which  the  capillary  is  opened,  the  second  instalment  of  bromine 
added  through  a  long  capillary  tube,  and  the  tube  after  being  resealed  is 
heated  as  before. 

Opening  Sealed  Tubes. — The  greatest  possible  care  must  be  observed  in 
handling  an  unopened  tube.  It  must  never  be  removed  from  its  pro- 
tecting case  for  examination  or  for  any  other  purpose.  It  must  not  be 
opened  until  perfectly  cold,  and  when  opening  it  is  held  in  such  a  position 
that  no  one  can  be  injured  should  it  burst. 

When  cold,  the  protecting  case  of  iron  is  withdrawn  from  the  furnace 
and  held  in  one  hand.  The  cap  (if  present)  is  unscrewed,  and  while  the 
iron  tube  is  held  in  a  slightly  inclined  position  so  that  the  capillary  is 
somewhat  higher  than  the  other  end,  the  capillary  is  made  to  project 
beyond  the  iron  case  by  giving  the  cylinder  a  slight  jerk.  The  part  of  the 
iron  cylinder  near  the  open  end  and  which  is  gripped  with  the  hand,  is 
wrapped  round  with  a  cloth.  The  extreme  end  of  the  capillary  is  then 
gradually  heated  in  a  Bunsen  flame.  If  pressure  exists  inside,  the  end  of 
the  capillary  is  blown  open  on  softening,  provided  there  is  no  obstruction 
in  the  capillary.    If  there  is  obstruction  it  may  be  removed  by  heating. 

Under  certain  conditions,  as,  for  instance,  when  the  tube  contains  an 
explosive  mixture  of  gases  (which  sometimes  happens  when  phosphorus 
and  hydriodic  acid  are  used)  or  when  it  is  desired  to  collect  the  gaseous 
products,  the  end  of  the  capillary  is  carefully  broken  off  with  pincers  or 
tongs — in  the  latter  case  inside  a  piece  of  pressure  tubing  connected 
with  a  suitable  gas  receiver. 

After  the  capillary  is  opened,  the  tube  is  removed  from  the  iron  case, 
and  the  conical  end  broken  off  in  the  following  manner.  A  deep  file  mark 
is  made  across  the  tube  about  1  cm.  below  the  shoulder,  and  the  scratch 
is  touched  with  the  pointed  end  of  a  drawn-out  glass  rod  which  has  been 


42 


SYSTEMATIC  ORGANIC  CHEMISTRY 


previously  heated  to  redness  in  a  blowpipe  flame.  In  the  majority  of 
cases  a  crack  forms  at  the  file  mark,  and  this  may  be  led  round  the  tube  by 
touching  the  glass  immediately  in  front  of  the  crack  with  the  heated  point 
of  the  glass  rod.  If  the  thick  end  of  a  glass  rod  is  used  in  these  operations, 
the  crack  may  form  longitudinally  on  the  tube.  A  piece  of  wire,  bent  to 
the  shape  of  the  tube  and  heated  to  redness,  may  be  employed  in  place  of 
the  heated  glass  rod. 

Another  method  which  is  not  so  liable  to  cause  splintering  at  the  cut  is 
the  following.    The  file  mark  is  made  as  before.    Two  pieces  of  wet  filter 

paper  are  rolled  round 
the  tube,  one  on  each 
side  of  the  file  mark  and 
about  0-5  cm.  apart. 
The  space  between  the 
papers  is  then  heated 
by  gradually  bringing 
it  into  a  pointed  blow- 
pipe flame,  the  tube 
being  rotated  the  while. 
If  the  tube  does  not 
crack  at  once,  it  is 
given  a  few  turns  in 
the  flame,  after  which 
the  heated  portion  is 
moistened  with  a  few 
drops  of  water,  when 
the  breaking  off  follows 
with  certainty.  In  ana- 
lytical work  this  latter 
method  of  opening 
should  be  employed,  as 
it  is  important  to  avoid 
the  mixing  of  frag- 
ments of  glass  with  the 
contents  of  the  tube. 
The  tube  is  then  emp- 
tied of  its  contents. 
(b)  Autoclaves. — These  are  closed  vessels  made  of  iron,  bronze  or  copper. 
Those  in  common  use  are  made  from  cast  steel,  and  hence  are  capable  of 
standing  great  pressure.  Such  vessels  are  not  suited  for  heating  mixtures 
of  a  resultant  acid  reaction,  but  may  be  used  for  mixtures  which  are  of 
neutral  or  alkaline  reaction.  When  acidic  substances  are  being  dealt  with, 
autoclaves  covered  on  the  interior  with  a  resistant  enamel  are  used,  but 
unfortunately  few  enamels  are  very  durable  and  in  consequence  the  vessel 
has  to  be  re-enamelled  at  intervals.  Of  the  special  alloys  which  are  used 
for  autoclaves,  those  containing  1 — 3%  of  Ni  which  are  highly  resistant 
to  alkalis,  and  those  containing  12%  Si  and  4 — 6%  Al  (Tantiron)  which 
are  practically  unattacked  by  acids,  are  the  most  important.    Fig.  40 


Fig.  40. 


APPARATUS  AND  METHODS 


43 


represents  a  form  of  autoclave  which  is  commonly  used  for  experi- 
mental purposes.  The  body  B  of  the  autoclave  is  immersed  in  an  oil  or 
metal  bath.  Along  the  flange  of  the  body  there  runs  a  circular  groove  of 
rectangular  section  which  is  filled  with  lead  (molten  lead  run  in  and 
allowed  to  solidify).  On  the  lower  surface  of  the  flange  of  the  lid  there  is  a 
projecting  ring  which  fits  neatly  into  the  lead-filled  groove,  and  when  the 
screws  between  the  body  and  lid  are  tightened,  a  pressure-tight  joint  is 
formed  at  the  lead  ring.  In  order  to  secure  a  proper  joint,  judicious 
tightening  of  the  screws  (these  should  run  easily  at  first)  is  necessary.  To 
begin  with,  one  nut  is  screwed  home  with  the  hand,  the  nut  diametrically 
opposite  is  similarly  treated,  these  are  then  alternately  given  a  few  turns 
with  a  wrench  until  they  are  moderately  tight.  The  intervening  nuts  are 
then  screwed  home,  each  one  a  little  at  a  time  so  as  to  maintain  as  far  as 
possible  a  uniform  pressure  over  the  whole  surface  of  the  lead  ring.  This 
done,  a  further  tightening — which  may  be  repeated  a  few  times — is  given  to 
all  the  nuts,  going  round  them  in  circular  fashion.  During  the  heating, 
the  nuts  should  be  tested  from  time  to  time,  and  tightened  if  necessary. 
The  lid  of  the  autoclave  is  provided  with  two  openings — one  for  a  ther- 
mometer tube,  and  another  for  a  pressure  gauge,  each  of  which  is  fixed  by 
a  screw  pressure-tight  joint ;  sometimes  there  is  a  third  opening  for  a 
safety  valve,  but  with  a  tested  autoclave  bought  from  a  reliable  firm,  a 
safety  valve  is  unnecessary,  and  often  an  encumbrance.  Such  autoclaves 
should,  however,  be  frequently  tested  by  engineers. 

It  is  often  convenient  to  place  inside  the  body  of  an  autoclave  a  neat 
fitting  pot  of  lead  or  enamelled  metal.  The  space  between  the  two  vessels 
may  be  filled  with  molten  solder  or  molten  lead,  but  in  many  cases  no  such 
filling  is  used.  The  inner  vessel  serves  to  protect  the  main  body  of  the 
apparatus,  and  its  easy  removability  (when  no  filling  is  used) — on  the 
small  experimental  scale  at  any  rate — can  be  utilised  in  the  charging  and 
the  emptying  of  the  apparatus.  During  the  operation  of  heating,  oil  or 
mercury  sufficient  to  cover  the  bulb  of  a  thermometer  is  placed  in  the 
thermometer  tube.  Autoclaves  are  made  in  various  sizes  with  capacities 
ranging  from  half  a  litre  up  to  a  few  thousand  litres.  Those  which  are 
provided  with  stirring  gear  are,  of  course,  the  more  efficient,  and  details  of 
these  may  be  obtained  from  the  catalogues  of  well-known  manufacturers. 
The  limits  of  temperature  and  pressure  are  about  300°  C.  and  60  atmo- 
spheres, and  the  greatest  charge  should  not  be  more  than  about  75%  of  the 
volume  of  the  vessel.  Temperature  of  the  outer  bath,  in  which  a  ther- 
mometer is  kept  immersed,  should  be  about  30°  higher  than  the  internal 
temperature.  The  screws  must  not  be  loosened  so  long  as  there  is  any 
pressure  indicated  on  the  gauge.  When  a  charge  contains  ammonia  or 
develops  ammonia  on  heating,  a  manometer  fitted  with  an  iron  and  not 
with  a  bronze  tube,  must  be  used,  since  ammonia  vapours  rapidly  destroy 
copper  or  bronze  tubes. 

Density  of  Liquids. 

The  density  of  a  liquid  is  most  easily  determined  by  means  of  vessels 
known  as  pyknometers,  the  volume  of  which  need  not  exceed  1  c.c. 


44 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Fig.  41. 


Perkin's  modification  (Fig.  41)  of  the  Sprengel  pyknometer  is  well  adapted 
for  small  quantities  of  liquid  and  also  for  volatile  liquids.  The  apparatus 
which  usually  has  a  volume  of  2 — 10  c.cs.  consists 
of  a  U-tube,  the  limbs  of  which  are  drawn  out  to 
capillaries  and  bent  as  shown.  On  limb  A  a  small 
bulb  is  blown,  and  below  this  a  ring  is  etched 
round  the  capillary.  The  ends  of  the  capillaries  are 
fitted  with  loose  glass  caps. 

The  apparatus  is  cleaned  and  dried  by  washing 
successively  with  water,  alcohol,  and  ether,  and 
then  drawing  air  through  the  tube.  The  apparatus 
is  first  weighed  empty,  being  suspended  from  the 
beam  of  a  balance  by  a  piece  of  platinum  wire. 
Liquid  is  then  drawn  into  the  vessel  through  B 
until  the  bulb  on  A  is  half  full.  The  apparatus  is 
immersed  in  a  bath  at  constant  temperature— ice 
and  water  serves  for  0°,  while  a  thermostat  should  be  used  for  higher 
temperatures.  After  standing  in  the  bath  for  some  time,  the  apparatus 
is  inclined  until  limb  B  assumes  a  horizontal  position  ;  a  piece  of  filter 
paper  applied  to  the  end  of  this  limb  is  allowed  to  absorb  liquid  until  the 
meniscus  on  limb  B  sinks  to  the  etched  mark.  The  apparatus  is  then 
returned  to  a  vertical  position,  the  glass  caps  are  replaced  on  the  limbs, 
and  after  removing  from  the  bath  the  whole  is  carefully  dried  with  a 
good  cloth  and  weighed.  Afterwards  the  apparatus  is  cleaned  and  dried, 
and  the  operation  repeated,  using  distilled  water.  , 
If  both  operations  are  carried  out  at  the  same  temperature — 

W 

The  approximate  density  ==  — 

where  W  =  weight  of  liquid, 
and    Wx  =  weight  of  water. 

W 


The  absolute  density  ( D 


x  D, 


4/  Wj 
where  D  =  density  of  water  at  4°, 

temperature  of  operations. 


^nd 


The  Polarimeter. 

The  polarimeter  is  used  for  determining  the  specific  rotations  of  optically 
active  substances  and  also  for  determining  concentrations  of  solutions  of 
optically  active  substances  of  known  specific  rotation. 

The  polarimeter  con- 
is    sists  of  two  Nicol  prisms 
I    N  and  Nx  (Fig.  42)  set 
J    at  a  distance  from  one 
another  and  on  a  common 
axis.   Nx  is  the  polariser 
and  N  the  analyser.     The  polarimeter  tube  T,  containing  a  definite 


0  ID  S 


P  N, 


Fig.  42. 


APPARATUS  AND  METHODS 


45 


length — usually  10  or  20  cms. — of  liquid  is  placed  between  the  two 
Nicols.  Monochromatic  light  must  be  used,  generally  that  from  a  sodium 
flame  F  being  employed.  The  light  from  F  passes  first  through  a  bichro- 
mate cell  C  in  order  to  give  the  pure  sodium  D  light,  then  through  a  lens 
to  the  polariser.  In  the  Laurent  polarimeter  a  thin  quartz  plate  P  is 
inserted  to  cover  half  the  field.  In  the  Lippich  type  a  small  Nicol  prism 
or  two  Nicol  prisms  are  used  instead  of  a  quartz  plate  to  cover  part  of  the 
field  ;  and  this  instrument  possesses  the  advantage  that  it  can  be  used 
with  light  of  any  wave  length. 

Light  vibrating  in  only  one  plane  passes  through  the  polarimeter  tube 
to  the  analyser  N,  which  can  be  rotated  about  the  main  axis.  The  eyepiece 
at  E  consists  of  a  system  of  lenses  for  focussing. 

The  sodium  flame  produced  from  common  salt  or  borax  is  adjusted  to 
give  a  maximum  of  light,  the  tube  T  being  removed  for  the  time  being. 
The  polariser  Nx  is  fixed  in  position.  The  illuminated  split  disc  is  then 
focussed  from  the  eyepiece  E,  and  the  analyser  rotated  until  the  whole  field 
is  of  uniform  intensity.  The  reading  as  indicated  on  a  circular  disc  fitted 
with  a  vernier  attached  to  the  eyepiece  is  taken  as  the  zero  reading.  This 
reading  should  be  determined  before  every  experiment.  The  substance  of 
which  the  specific  rotation  is  to  be  determined  is  placed  in  a  clean  dry 
polarimeter  tube  in  the  form  of  liquid  or  of  solution  so  as  to  completely 
nil  the  tube.  The  tube  is  then  placed  in  position  in  the  polarimeter  ;  the 
analyser  is  again  turned  until  the  intensity  of  illumination  on  each  half  of 
the  disc  is  equal.  The  angle  is  again  read  on  the  scale,  and  this  reading, 
minus  the  zero  reading,  gives  the  angle  of  rotation,  aD.  The  temperature 
at  which  the  observation  is  made  should  be  noted ;  in  some  cases  a 
jacketed  polarimeter  tube,  through  which  water  at  a  definite  temperature 

is  circulated,  is  used.    The  specific  rotation —     J  ^ — at  temperature  t 

of  a  pure  liquid  is  calculated  from  the  formula  : — 


a  =  angle  of  rotation. 

I  =  length  in  decimetres  of  liquid  in  polarimeter  tube. 
d  =  density  of  liquid  at  t°. 

The  specific  rotation  of  an  optically  active  compound  in  a  pure  solvent 
may  be  calculated  from  the  formula  : — 


c  =  gms.  of  active  compound  in  100  c.cs.  of  solvent. 
p  =  percentage  of  solute  by  weight. 

If  the  substance  turns  the  plane  of  polarisation  to  the  right,  i.e.,  clock- 
wise, it  is  said  to  be  dextro-rotatory,  and  if  to  the  left,  laevo-rotatory.  (See 
Findlay,  "  Practical  Physical  Chemistry,"  p.  112.) 


Hi 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Fig.  43. 


Apparatus  for  certain  Catalytic  Preparations. 

The  following  apparatus  (Fig.  43)  serves  for  such  a  large  number  of 
catalytic  preparations  that  it  may  be  considered  general  apparatus  (see 
acetaldehyde,  acetone  and  hexahydro-phenol).    The  catalyst,  generally 

distributed  over  some 
bulky  material  (e.g., 
pumice,  etc.),  is  placed 
in  a  combustion  tube 
which  is  ins  ert  ed 
through  two  holes  in 
the  ends  of  a  long  cylin- 
drical air  bath  made  of 
tin  or  light  sheet  iron. 
The  air  bath  is  of  such  a 
length  (about  75  cms.) 
that  it  fits  on  an  ordin- 
ary combustion  furnace 
by  which  it  is  heated  ; 
its  diameter  is  usually  about  20  cms.,  and  there  are  two  openings  in  the  top 
for  the  insertion  of  thermometers.  Nitrogen-filled  thermometers  or 
thermo-couples  are  necessary  for  temperatures  of  400°  and  above. 

When  a  liquid  is  used  in  the  reaction  it  may  be  led  into  the  tube  in  the 
following  ways,  the  method  selected  depending  on  the  requirements  of  the 
reaction  : — 

1.  A  distilling  flask  is  attached  to  the  inlet  end  of  the  tube  and  the  liquid 
distilled  over,  or  it  may  be  evaporated  over  in  a  current  of  gas. 

2.  A  silica  distilling  flask  surrounded  by  an  air  bath  (a  tin  or  iron  box 
covered  with  a  card  of  asbestos)  is  connected  to  the  tube,  the  bath  being 
heated  to  a  high  temperature,  say  300° — 400°.  The  liquid  is  dropped  into 
the  silica  flask  from  a  dropping  funnel  inserted  through  a  cork  in  the  neck 
of  the  flask  ;  by  this  means  the  rate  of  passage  of 

vapours  over  the  catalyst  may  be  controlled,  and 
further,  the  vapours  are  at  a  high  temperature 
before  coming  into  contact  with  the  catalyst. 

3.  A  bent  dropping  funnel  is  inserted  through  a 
cork  in  the  inlet  end  of  the  combustion  tube,  the 
first  15  cms.  of  which  is  loosely  packed  with 
asbestos  and  is  kept  outside  the  air  bath.  The 
liquid  is  allowed  to  drop  in  slowly  from  the  funnel. 
A  small  flame  is  lighted  under  the  tube  where  the 
liquid  drops,  and  the  flames  gradually  increase  in 
size  as  the  catalyst  is  approached  ;  this  precaution 
is  to  prevent  breakage. 

A  solid,  if  easily  volatile,  may  be  treated  as 
for  a  liquid.  In  some  cases  it  may  be  steam  distilled  over  the  catalyst. 

Most  experiments  of  this  kind  require  efficient  apparatus  for  condensing 
the  products  of  reaction  ;  owing  to  the  high  temperature  it  is  generally 


Fig.  44. 


APPARATUS  AND  METHODS 


17 


advisable  to  pass  these  first  through  an  empty  flask  and  then  through 
some  efficient  type  of  condenser.  The  condensing  apparatus  may  be 
attached  to  the  exit  end  of  the  combustion  tube  by  means  of  a  cork  and 
delivery  tube,  or  the  exit  end  of  the  combustion  tube  may  be  bent  and 
drawn  out  after  the  shape  of  an  adapter. 

Addition  Tube. 

The  Y-shaped  tube  (Fig.  44)  is  a  most  convenient  apparatus  through 
which  to  make  additions  to  a  mixture  which  is  being  heated  under  a  reflux 
condenser.  It  is  particularly  useful  for  the  addition  of  solids  (for  example, 
sodium — see  p.  361).  For  the  addition  of  liquids  a  dropping  funnel  is 
introduced  through  a  cork  in  the  upright  limb. 


PART  II 


CHAPTER  III 

the  linking  of  carbon  to  carbon  , 

Hydrogen  Compounds 

In  this  section  are  described  those  preparations  in  which  carbon  atoms 
are  caused  to  unite  with  one  another.  It  is  this  property  whereby 
carbon  atoms  unite  to  form  molecules  of  seemingly  unlimited  com- 
plexity, which  has  led  to  the  study  of  the  carbon  compounds  being  made 
a  special  branch  of  chemistry,  and  these  reactions  are,  theoretically  at  any 
rate,  the  most  important  of  all  those  discussed.  They  are  often  known 
as  "  nucleus  syntheses." 

Reaction  I.  Passage  of  the  Vapour  of  certain  Hydrocarbons  through  a 
red-hot  Tube.  (A.,  230,  5.) — A  large  number  of  hydrocarbons  condense 
to  form  hydrocarbons  of  higher  molecular  weight  when  their  vapour  is 
passed  through  a  red-hot  tube.  The  method,  however,  is  only  of  theoretical 
importance  for  the  yield  is  in  most  cases  small  owing  to  incomplete  con- 
version, and  to  the  formation  of  a  large  number  of  by-products.  Benzene 
has  been  obtained  from  acetylene  in  this  way  ;  benzene  itself,  and  diphenyl 
methane  treated  in  a  similar  manner  give  diphenyl  and  nuorene  respec- 
tively. 

Heat 

R.H.  +  H.R.   >   R.R.  +  H2, 

where  R.H.  is  a  hydrocarbon. 
Preparation  1. — Diphenyl  (Phenyl-benzene). 

C6H5.C6H5.       C12H10.  154. 

Method  I. — In  this  experiment  the  apparatus  shown  in  Fig.  45  is  used. 
The  flask,  of  about  1J  litres  capacity,  contains  500  gms.  of  benzene  kept 
boiling  by  means  of  a  water  bath.  The  flask  is  provided  with  a  cork 
having  two  perforations,  through  one  of  which  the  tube  a  passes  while  < 
the  second  accommodates  the  tube  b.  This  leads  to  the  iron  tube  R  (a 
wrought-iron  gas  pipe  of  1  metre  length,  and  20  mms.  internal  diameter), 
which  is  filled  with  pieces  of  pumice,  and  heated  by  means  of  a  com- 
bustion furnace  or  a  Fletcher's  gas  furnace  to  a  bright  red  heat.  From  the 
flask  the  benzene  vapour  passes  into  the  glowing  tube,  and  is  here  partially 
converted  into  diphenyl,  hydrogen,  and  other  products.  The  unchanged 
benzene  and  the  volatile  diphenyl  pass  through  the  tube  e  into  the  con-  I 
denser  K  and  flow  from  it  through  a  back  into  the  flask.   The  tube  a  dips 

48 


THE  LINKING  OF  CARBON  TO  CARBON 


49 


below  the  level  of  the  liquid,  and  at  d  has  a  tube  sealed  on  for  the  escape 
of  the  hydrogen.  The  operation  is  carried  on  for  from  6  to  10  hours,  the 
apparatus  acting  auto- 
matically. The  flask 
now  contains  a  fairly 
concentrated  solution 
of  diphenyl  in  ben- 
zene. The  latter  is 
removed  on  a  water 
bath,  and  the  residue 
is  fractionated.  The 
part  passing  over 
above  150°  solidifies 
in  the  receiver,  and 
consists  of  almost  pure 
diphenyl.  It  may  be 
purified  by  crystalli- 
sation from  alcohol. 
The  yield  is  greatly 
dependent  on  the  tem- 
perature of  the  iron 
tube.  With  a  low  gas 
pressure  the  ordinary  pIG>  45> 

combustion  furnace  is 

almost  useless  ;  in  that  case  it  is  better  to  substitute  a  Fletcher's  gas 
furnace  or  a  charcoal  furnace  for  it. 


2CJL 


C6H5.C6H5  +  H2 


Yield.— Up  to  20%  theoretical  (100  gms.).  D.  f  0-9845.  (Z.  Ch.,  1866, 
707  ;  A.,  230,  5.) 

This  "  thermal  condensation  "  can  also  be  brought  about  by  exposing 
the  vapour  of  benzene  to  the  action  of  a  wire  or  filament  kept  at  red  heat 
by  an  electric  current. 

Method  II. — The  apparatus  is  as  follows : — Two  copper  wires  pass 
tight-fitting  through  the  cork  in  the  neck  of  a  flask,  and  are  connected 
together  above  the  benzene  in  the  flask  by  a  coiled  platinum  wire,  25 
cms.  long  and  -2  mm.  in  diameter.  A  reflux  condenser  is  fitted  to  the  side 
tube  of  the  flask.  50  gms.  of  benzene  are  boiled  on  a  water  bath  in  the 
flask.  After  fifteen  minutes' boiling  the  air  in  the  flask  will  have  been 
expelled,  and  the  current  is  switched  on  and  regulated  by  means  of  a 
variable  resistance  so  that  the  platinum  spiral  glows  red  (4 — 4-5  amps.  ; 
8 — 10  volts).  A  battery  of  accumulators  can  be  used  as  a  source  of  current, 
or  the  latter  can  be  obtained  from  an  alternating  service  supply  at  110  or 
220  volts,  the  necessary  reduction  in  current  and  voltage  being  brought 
about  by  a  rheostat  or  a  bank  of  lamps.  In  the  latter  case  it  is  more 
economical  to  use  the  thread  of  a  carbon  lamp  instead  of  a  platinum  wire. 
After  five  hours  a  portion  of  the  benzene  will  have  been  converted  into 
diphenyl  under  the  action  of  red  heat.   The  unaltered  benzene  is  removed 


50 


SYSTEMATIC  ORGANIC  CHEMISTRY 


on  a  water  bath,  and  the  residual  liquid  fractionated  from  a  small  flask, 
the  portion  240°— 270°  being  collected  separately,  and  recrystallised  from 
alcohol  or  from  a  mixture  of  benzene  and  petroleum  ether — 

2C6H6  =  C6H5.C6H5  +  2H. 

Yield.— 22%  theoretical  (11  gms.)  Colourless  leaflets  ;  soluble  in  ben- 
zene ;  M.P.  71°  ;  B.P.  254°  ;  D.  f  0-9845.    (Z.  e.,  7,  903.) 


Fig.  46. 


Reaction  II.   Reduction  under  certain  Conditions  of  Aromatic  Ketones. 

(A.,  194,  310.) — When  aromatic  ketones  are  reduced  by  zinc  dust  in  the 
presence  of  glacial  acetic  acid  pinacones  are  formed  (see  p.  65). 

2C6H5.CO.C6H5  +  2H  =  (C6H5)2C.(OH).C(OH).(C6H5)2. 

If  hydrochloric  acid  is  added  the  reduction  goes  to  the  corresponding 
hydrocarbon ;  e.g.,  from  benzophenone  s-tetraphenylethane  is  obtained. 

2C6H5.CO.C6H5  +  6H  >  (C6H5)2.CH.CH.(C6H5)2. 

Reaction  III.  Oxidation  under  certain  Conditions  of  Lower  Hydro- 
carbons. (B.,  32,  432.) — In  this  reaction  two  molecules  of  a  hydrocarbon 
are  condensed  together  by  eliminating  hydrogen  by  means  of  an  oxidising 
agent.  Two  neutral  oxidising  agents,  potassium  persulphate,  and  lead 
oxide,  are  especially  useful  in  this  type  of  reaction.  The  former  is  used  in 
dilute  aqueous  solution,  at  a  temperature  of  about  100°  ;  to  obtain  results 
with  the  latter  much  higher  temperatures  are  necessary.  The  substance 
is  mixed  with  the  lead  oxide  and  heated  to  over  250°,  or  it  is  distilled  over 
heated  lead  oxide.  The  results  obtained  vary  with  the  temperature  and 
the  amount  of  lead  oxide  used,  e.g.,  fluorene  can  be  oxidised  to  either 


THE  LINKING  OF  CARBON  TO  CARBON 


51 


bidiphenylene- ethane  or  bidiphenylene-ethylene.  With  potassium  per- 
sulphate the  first  stage  only  is  reached. 


C6H4 


C6H4 

\ 

r,  / 

C6H4 

C6H4 

\ 

\ 
/ 

/ 
CfiH4 


CH  -  CH 


C6H4 
C6H4 


C6H4 


It  is  to  be  noted  that  to  obtain  practicable  yields  this  reaction  must  be 
confined  to  aromatic  hydrocarbons.  In  the  aliphatic  series  it  only  takes 
place  in  a  few  cases,  and  then  gives  but  a  yield  of  the  order  of  1%. 

Preparation  2. — Dibenzyl  (1-2  Diphenylethane). 


CfiHriCHo.CHo.CRH, 


C1dHn 


182. 


90  grns.  potassium  persulphate  (1  mol.)  are  dissolved  in  a  litre  of  water, 
and  to  this  is  added  60  gms.  (2  mols.)  of  toluene.  The  mixture  is  heated  on 
a  water  bath  for  4  hours  in  a  flask  fitted  with  good  agitation  and  a  reflux 
condenser  (see  Fig.  37).  The  oily  layer  is  then  separated,  dried  over 
calcium  chloride  and  fractionally  distilled,  the  fraction  270° — 280°  con- 
sisting of  dibenzyl  and  benzoic  acid  being  separately  collected.  The  earlier 
fractions  consist  of  toluene  and  benzaldehyde.  The  dibenzyl  fraction  is 
dissolved  in  ether  and  the  benzoic  acid  removed  by  shaking  with  dilute 
caustic  soda  solution.  The  ether  is  then  removed  on  the  water  bath,  and 
the  residue  recrystallised  from  dilute  alcohol. 

4C6H5.CH3  +  02^2C6H5CH2CH2C6H5  +  2H20. 

Yield. — 15%  theoretical  (9  gms.).  Colourless  monoclinic  needles  ;  M.P. 
51°— 52°  ;  B.P.  248°  ;  D.g  0-9752.    (B.,  32,  432,  2531.) 

Preparation  3.  —  Bi-diphenylene-ethane  (l-2-Di-(2-21-diphenylene)- 
ethane). 


CH 

i 

CH 


C26  H18. 


330. 


10  gms.  (2  mols.)  of  fluorene,  and  15  gms.  (excess)  of  lead  oxide  are 

E  2 


52 


SYSTEMATIC  OKGANIC  CHEMISTRY 


thoroughly  mixed  and  heated  with  slow  stirring  in  a  metal  crucible  in  a 
bath  till  the  temperature  of  the  latter  reaches  270°,  where  it  is  kept  for 
2  hours.  The  crucible  is  cooled  to  150°,  wiped  clean,  and  plunged  into 
cold  water.  The  contents,  which  are  by  this  means  loosened,  are  ground 
up,  extracted  with  boiling  benzene,  and  the  extract  concentrated  to  small 
bulk.  The  crystals  which  separate  are  recrystallised  from  benzene,  or 
glacial  acetic  acid.    The  mother  liquors  contain  unaltered  fluorene. 


+  H20 


Yield. — 50%  theoretical  (5  gms.).  Colourless  crystals  ;  slightly  soluble 
in  alcohol  and  ether ;  soluble  in  hot  benzene  and  glacial  acetic  acid  ; 
M.P.  246°.    (A.,  291,  6.) 

Reaction  IV.  (a)  Action  of  Dehydrating  Agents  on  a  Mixture  of  an 
Aromatic  Hydrocarbon  and  an  Aromatic  Alcohol.  (B.  6,  964.) — This 
reaction,  which  was  discovered  by  Baeyer,  gains  importance  from  its 
similarity  to  the  methods  used  in  preparing  such  substances  as  phenol- 
phthalein  and  fluorescein  (see  pp.  100,  378). 

Various  dehydrating  agents — concentrated  sulphuric  acid,  zinc  chloride, 
phosphorus  pentoxide — can  be  used.  Sulphuric  acid,  although  perhaps 
the  most  convenient,  has  the  disadvantage  that  it  tends  to  sulphonate 
the  aromatic  substances  employed.  At  a  low  temperature,  however, 
diphenylmethane  can  be  obtained  from  benzyl  alcohol  and  benzene.  At 
140°  phosphorus  pentoxide  condenses  benzene  and  diphenylcarbinol  to 
triphenylmethane  (see  B.,  7,  1204).  Not  only  substituted  benzyl  alcohols, 
but  even  mandelic  acid  can  be  brought  within  the  scope  of  the  reaction, 
while  in  place  of  benzene  its  nitro,  amino  or  phenolic  derivatives  may  be 
used. 


REjCH  ;OH  +  HI  Rn  =  RRjCHRu  +  H20. 


Preparation  4. — Diphenylmethane.  (Benzyl-benzene.) 

CH2.(C6H5)2.       C13H12.  168. 

A  mixture  of  equal  weights  of  concentrated  sulphuric  acid  and  glacial 
acetic  acid  is  run  into  a  mixture  of  10  gms.  (1  mol.)  of  benzyl  alcohol  (q.v.), 
27  gms.  (excess)  of  benzene  and  100  gms.  of  glacial  acetic  acid  until  most 
of  the  benzene  has  separated  on  the  surface.  After  12  hours,  500  gms.  of 
concentrated  sulphuric  acid  are  added  under  constant  cooling,  and  the 


THE  LINKING  OF  CARBON  TO  CARBON 


53 


mixture  again  allowed  to  stand  for  6  hours.  The  mass  is  then  poured  into 
water,  extracted  with  ether,  the  extract  dried  over  calcium  chloride,  and 
the  residue,  after  removing  the  ether  on  a  water  bath,  fractionated  under 
reduced  pressure,  the  fraction  174° — 176°  at  30  mms.  being  separately 
collected. 

C6H5.CH2OH  +  C6H6  =  C6H5.CH2.C6H5  +  H20. 

Yield. — 25%  theoretical  (4  gms.).  Colourless  oil ;  on  cooling  solidifies 
to  needle-shaped  crystals  ;  orange-like  odour ;  M.P.  26°  ;  B.P. 760  263° ; 
B.P.  30  175°  ;  D.  1  1-0056.    (B.,  6,  964.) 

Reaction  IV.   (b)  Action  of  Dehydrating  Agents  on  Certain  Ketones. 

(J.  pr.,  15,  129). — This  is  a  reaction  of  historical  interest,  for  it  was  by  its 
preparation  from  acetone  by  distillation  with  fairly  strong  sulphuric  acid 
that  the  symmetry  of  mesitylene  was  deduced,  and  from  it  the  orientation 
of  such  compounds  as  m-xylene  was  established.  It  will  be  noted  that 
though  a  high  temperature  is  used,  steric  hindrance  prevents  any  sul- 
phonation  of  the  mesitylene  formed. 

Besides  its  dehydrating  action,  the  purely  condensing  capabilities  of 
sulphuric  acid  should  not  be  overlooked.  Thus  methyl  acetylene  con- 
denses in  the  presence  of  sulphuric  acid  to  mesitylene. 

3CH3C  ■  CH  =  C6H3(CH3)3. 

Compare  the  action  of  heat  on  acetylene. 
Preparation  5— Mesitylene.  (s-Trimethylbenzene.) 

C6H3(CH3)3[1:3:5].  120. 

400  gms.  of  clean  dry  sand  are  placed  in  a  2-litre  retort  connected  with 
a  condenser.  250  gms.  (3  mols.)  of  acetone  are  added,  and  then  a  cooled 
mixture  of  560  gms.  of  concentrated  sulphuric  acid  and  150  gms.  of  water 
are  run  in,  in  a  slow  continuous  stream,  the  retort  being  meantime  cooled 
in  cold  water.  After  24  hours'  standing,  the  mixture  is  slowly  distilled, 
directly  or  in  steam.  When  oily  drops  appear  in  the  neck  of  the  retort, 
the  receiver  is  changed  and  the  distillate  collected  until  only  very  small 
quantities  of  the  oil  appear.  Meanwhile  the  colour  of  the  liquid  in  the 
retort  changes  to  deep  brown,  and  finally  to  black,  sulphur  dioxide  is 
evolved,  and  the  mass  froths  up  considerably.  The  upper  yellowish 
layer  of  the  distillate  is  separated  from  the  lower  aqueous  layer,  washed 
with  caustic  soda  and  water,  and  dehydrated  over  calcium  chloride.  It 
is  then  fractionated,  the  fraction  100° — 200°  being  redistilled  four  times 
over  thin  slices  of  metallic  sodium,  when  about  two-thirds  of  it  is  obtained 
as  pure  mesitylene  coming  over  at  161° — 166°. 

3CH3.CO.CH3  =  C6H3(CH3)3  +  3H20. 

Yield. — -Variable,  about  25%  theoretical  (40  gms.).  Colourless,  strongly 
refracting  liquid  ;  B.P.760  1  63°  ;  D.J  0-881 ;  D.1,0  0-8694.  (J.  pr.,  15,  129  ; 
A.,  147,  143  ;  278,  260  ;  Bl.,  40,  267  ;  Am.  Soc,  15,  256  ;  20,  807.) 

Acetophenone  condenses  in  a  manner  similar  to  acetone  if  it  is  heated 


54 


SYSTEMATIC  OBGANIC  CHEMISTEY 


with  phosphorus  pentoxide,  or  better  if  saturated  with  dry  hydrogen 
chloride  at  ordinary  temperatures.  s-Triphenylbenzene  is  deposited  after 
standing  for  several  days  in  a  warm  place  ;  by  resaturating  the  mother 
liquors,  yields  of  up  to  50%  can  be  obtained.  Two  isomeric  s-triphenyl- 
benzenes  are  known  (B.,  7,  1123  ;  23,  2533  ;  C.,  1900,  II.,  255.) 


C6H5 


HC 

m 

o  i 


CgH; 


0 

CH 


C — CfiH, 


CH 


CfiH, 


CH 


— C6H5 


C  H2 


CH 


H 

Reaction  V.   Cinnamic  Condensation  and  Elimination  of  Carbon  Dioxide. 

(Am.  Soc,  1,  313.) — This  is  an  extension  of  Perkin's  reaction,  and  depends 
on  the  fact  that  when  benzaldehyde  and  phenyl-acetic  acid  are  condensed 
in  the  usual  way,  the  unsaturated  acid  thus  formed  is  unstable,  and  loses 
carbon  dioxide,  giving  stilbene. 

C6H5.CHO  +  H2C.(C6H5)COOH  -> 

C6H5CH  :  C(C6H5)COOH  ->  C6H5CH  :  CH.C6H5. 

Technically  this  method  is  of  no  importance,  as  the  hydrocarbon  is 
obtained  from  coal-tar. 

Reaction  VI.  (a)  Action  of  certain  Anhydrous  Metallic  Halides  on  a 
Mixture  of  an  Aromatic  Hydrocarbon  and  an  Akyl  Halide.  (Friedel-Crafts.) 

(C.  r.,  1877,  1450.)— The  "  Friedel-Crafts  "  reaction,  of  which  the  above 
illustrates  one  phase,  is  one  of  the  most  important  condensing  reactions 
known  to  organic  chemistry.  Applied  to  the  production  of  aromatic 
hydrocarbons  and  their  derivatives,  the  action  consists  in  the  catalytic 
use  of  anhydrous  aluminium  chloride  for  condensing  an  aromatic  hydro- 
carbon or  its  derivatives  with  a  chlorine  or  bromine  compound.  Halogen 
acid  is  always  evolved,  and  the  product  is  a  compound  with  aluminium 
chloride  which  decomposes,  yielding  the  required  compound  on  addition 
of  water.  Not  only  does  the  reaction  proceed  without  the  Use  of  heat  in 
most  cases,  but  frequently  it  must  be  moderated  by  using  a  large  excess  of 
the  hydrocarbon,  or  better  by  diluting  with  some  neutral  solvent,  such  as 
ligroin,  carbon  disulphide,  or  nitrobenzene.  The  two  former  diluents 
automatically  keep  down  the  temperature  to  their  boiling  points;  the 
latter  has  the  especially  useful  property  of  dissolving  anhydrous  alu- 
minium chloride.  If  a  hydrocarbon  derivative  is  used,  coupling  takes 
place  in  the  para  position,  or,  if  that  is  occupied,  in  the  ortho,  but  the 
yield  suffers.    In  place  of  aluminium  chloride,  in  some  cases  aluminium 


THE  LINKING  OF  CARBON  TO  CARBON 


55 


bromide  (D.R.P.,  126421),  aluminium  foil  and  hydrogen  chloride  (B.,  28, 
1136),  or  mercuric  chloride  (see  Reaction  VI.  (b)  ),  ferric  chloride,  zinc 
chloride  (B.,  30, 1766),  or  the  aluminium-mercury  couple  (Reaction  VI.  (c) ) 
can  be  used.  (See  also  C.  r.,  84,  1392  ;  B.,  18,  2402  ;  33,  815.  For  other 
uses  of  this  reaction,  see  pp.  80,  115.) 

The  methods  employed  vary  but  little.  The  aluminium  chloride  is 
slowly  added  to  a  mixture  of  the  hydrocarbon  and  the  alkyl  halide,  or  the 
alkyl  halide  is  added  to  a  mixture  of  the  other  two.  The  latter  process 
is  most  used  in  the  case  of  volatile  halides  which  are  led  in  gaseous  form 
into  the  mixture  of  the  other  two  components,  for  a  time  which  varies  as 
the  number  of  alkyl  groups  it  is  desired  to  introduce. 

EC1  +  A1C13  =  E.CIAICI3 
R.C1.A1CI3  +  RJi  =  RI^AlClg  +  HC1 
RRjAlClg  +  H20  =  RRX  +  A1C13  -f  H20. 

Note. — Bottles  filled  with  aluminium  chloride  have  frequently  a  high 
internal  pressure  and  must,  therefore,  be  opened  with  great  care,  being 
covered  with  a  cloth  while  so  doing. 

For  some  anomalies  in  the  behaviour  of  aluminium  chloride  as  compared 
with  that  of  aluminium  bromide,  see  A.?  225,  155. 

Preparation  6. — Triphenylmethane.  (Methenyl-triphenyl.) 

CH.(C6H5)3.       C19H16.  244. 

40  gms.  (1  mol.)  of  chloroform  which  has  stood  for  12  hours  over  calcium 
chloride  is  mixed  with  200  gms.  (excess)  of  similarly  treated  benzene  in  a 
retort  connected  to  an  upright  condenser.  The  operation  is  carried  out 
in  a  fume  cupboard.  30  gms.  of  anhydrous  aluminium  chloride  (see 
p.  503)  are  added  in  5-gm.  lots  every  5  minutes  with  constant  shaking. 
The  reaction  is  completed  by  boiling  for  half  an  hour  on  a  water  bath,  the 
retort  cooled,  and  its  contents  very  cautiously  poured  into  an  equal  volume 
of  ice-cold  water.  The  upper  layer  of  triphenylmethane  dissolved  in 
benzene  is  separated,  dried  over  calcium  chloride,  the  benzene  removed 
on  a  water  bath,  and  the  residue  fractionated  to  200°.  It  is  then  distilled 
under  reduced  pressure  from  a  retort  without  a  condenser.  Impure 
triphenylmethane  first  distils  and  then  the  distillation  slackens.  The  retort 
is  more  strongly  heated  till  the  distillate  no  longer  solidifies  on  cooling. 
The  crude  triphenylmethane  in  the  receiver  is  twice  recrystallised  from 
hot  benzene,  heated  on  a  water  bath  to  remove  "  benzene  of  crystallisa- 
tion "  and  finally  recrystallised  from  hot  alcohol. 

CHCI3  +  3C6H6  =  CH(C6H5)3  +  3HC1. 

Yield. — 33%  theoretical  (25  gms.).  Colourless  rhombic  plates  ;  M.P. 
92°  ;  B.P. 760  350°  ;  D.  g 1-0568.  The  compound  with  benzene  has  the 
formula  C9H16.C6H6. 

Note. — The  aluminium  chloride  used  must  be  recently  made  and  of  good 
quality,  otherwise  it  must  be  resublimed  from  a  retort,  as  it  is  essential  it 
should  be  perfectly  anhydrous.  (C.  r.,  1877,  1450;  B.,  26,  1961 ;  BL,  37, 
6  ;  A.,  197,  252.) 


56 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Reaction  VI.  (b)  Action  under  certain  conditions  of  Aluminium  and 
Mercuric  Chloride  on  a  Mixture  of  an  Aromatic  Hydrocarbon  and  an  Alkyl 
Halide.  (J.  C.  S.,  117,  1335.)— This  is  a  development  of  the  Friedel-Crafts 
reaction  which  has  lately  yielded  some  very  interesting  results.  As  far 
back  as  1895  an  attempt  to  use  a  mixture  of  aluminium  powder  and 
mercuric  chloride  in  the  ordinary  Friedel-Crafts  reaction  ended  in  failure 
(B.,  28,  1139).  Later  (B.,  37,  1560),  it  was  proved  that  mercuric  chloride 
and  aluminium  in  benzene  or  toluene  formed  compounds  of  the  type 
C6H6.AlCl3.HgCl.  It  was  by  the  use  of  these  double  compounds 
that  the  secondary  reactions,  which  caused  the  failure  of  the  earlier 
attempts,  were  avoided  and  some  very  interesting  condensations 
brought  about.  In  the  formation  of  the  catalyst  the  following  reaction 
occurs  : 

C6H6  +  Al  +  2HgCl2^  C6H6.AlCl3.HgCl  +  Hg. 

An  excess  of  mercuric  chloride  must  be  used  to  prevent  the  mercury 
iberated  amalgamating  with  the  aluminium,  for  the  couple  so  formed 
would  act  concurrently  with,  but  in  a  different  manner  to,  the  double 
compound  (see  the  next  reaction). 

Applied  to  the  synthesis  of  hydrocarbons  the  following  results  have  been 
obtained  by  this  new  method.  9  :  10-Diphenyl-9  :  10-dihydroanthracene 
is  formed  by  the  condensation  of  benzene  and  chloroform,  whilst  in  the 
ordinary  Friedel-Crafts  reaction  (A.,  194,  254 ;  227,  107)  triphenyl- 
methane  (Preparation  6)  is  the  main  product,  traces  of  chloraryl- 
methanes  and  tetraphenylethane  (B.,  26,  1952)  being  also  formed.  The 
same  compound  was  also  obtained  from  benzal  chloride  and  benzene. 
Carbon  tetrachloride  and  benzene  give  9:9  :  10  :  10-tetraphenyl-9  :  10- 
dihydroanthracene  as  do  also  phenylchloroform  and  benzene.  In  the 
older  reaction  triphenylchloromethane  (p.  425)  is  the  chief  product. 

Chloroform  and  toluene  yield  by  this  process  dimethyl-9  :  10-ditolyl- 
9  :  10-dihydroanthracene  ;  using  aluminium  chloride,  tetratolylethane 
has  been  prepared  (B.,  14,  1530).  Finally  benzal  chloride  and  toluene 
yield  dimethyl-9  :  10-diphenyl-9  :  10-dihydroanthracene. 

EH 

+  , 

C12CH  K 

\  I 

\  I 
C6H5  CH 


C6H5 


+ 


C6H4  C6H 


CHCL 


+  CH 
RH  | 

I 

R 


For  other  applications  of  this  reaction  see  pp.  84, 115. 


THE  LINKING  OF  CARBON  TO  CARBON 


57 


Preparation  7.  -  9  : 10-Diphenyl  -  9  : 10  -  dihydroanthracene  (y1  -  y2 
Diphenylanthracene  hydride). 

CH 


332. 


|  CH 
C6H5. 

To  prepare  the  catalyst,  13  gms.  (excess)  of  dry  benzene  and  20  gms. 
(excess)  of  mercuric  chloride  are  treated,  gradually,  in  a  flask  fitted  with 
a  reflux  condenser,  with  1  gm.  of  aluminium  powder,  the  flask  being  mean- 
while vigorously  shaken  and  occasionally  cooled  in  ice-water.  A  green 
crystalline  mass  separates,  and  the  reaction  is  completed  by  immersing 
the  flask  in  tepid  water  for  half  an  hour.  The  mercury  liberated  in  the 
'  reaction  is  removed,  and  the  catalyst  is  then  ready  for  use. 

9  gms.  (2  mols.)  of  chloroform  are  added  drop  by  drop  through  the  con- 
j  denser,  and  the  flask  left  at  ordinary  temperature  for  2  hours,  heated  for 
an  hour  at  40°  and  then  for  an  hour  at  40° — 50°.  During  the  whole  course 
of  the  reaction  the  contents  of  the  flask  are  well  agitated  by  a  mechanical 
stirrer  (see  the  apparatus  shown  on  p.  37). 

On  cooling,  the  product  is  decomposed  with  ice  and  filtered.  From  the 
filtrate  a  deep-red  oil  separates,  from  which  all  unchanged  benzene  is 
evaporated,  and  the  residue  extracted  with  boiling  acetic  acid  containing 
a  little  water.  The  compound  which  separates  on  cooling  is  recrystallised 
from  dilute  alcohol,  and  then  repeatedly  from  acetone. 

The  same  compound  can  be  prepared  from  8  gms.  (2  mols.)  of  benzal 
chloride,  13  gms.  (excess)  of  benzene,  and  the  above  quantities  of  alu- 
minium and  mercuric  chloride.  The  reaction  is  completed  at  50° — 55°. 
Otherwise  the  details  are  as  already  described. 


C6H6 

+ 
CHC13 

CeHe  +    +       +  C6H6 
CHCI3 

+ 
C6H6 


C6H5 

I 

CH 

/\ 

C6H  /      ^C6H4  +  6HC1 

Yh 


C6H5. 

Colourless  crystals  ;  soluble  in  alcohol ;  M.P.  159°  (J.  C.  S.,  loc.  cit.)  ; 
M.P.  164-2°  (Am.  Soc,  13,  556).  Oxidised  with  chromium  trioxide 
in  glacial  acetic  acid  solution,  yields  anthraquinone  ;  gives  a  diacetyl 


58 


SYSTEMATIC  ORGANIC  CHEMISTEY 


derivative  on  heating  with  acetic  anhydride  and  pyridine  (J.  C.  S.,  117, 
1335). 

Reaction  VI.  (c)  Action  of  the  Aluminium — Mercury  Couple,  or  of 
certain  finely  divided  Metals  on  a  Mixture  of  an  Aromatic  Hydrocarbon  and 
an  Alkyl  Halide.  (J.  C.  S.,  67,  826.) — The  action  of  the  couple  is  analogous 
to  that  of  anhydrous  aluminium  chloride.  Zinc  dust  or  finely  divided 
copper  can  also  be  used. 

Preparation  8. — Diphenylmethane.  (Benzyl-benzene.) 

C6H5.CH2.C6H5.       C13H12.  168. 

1  gm.  of  freshly  prepared  aluminium-mercury  couple  (see  p.  503)  is 
added  to  65  gins,  (excess)  of  benzene  in  a  flask  attached  to  an  upright 
condenser,  the  whole  being  placed  in  a  fume  cupboard.  32  gms.  (1  mol.) 
of  benzyl  chloride  are  slowly  dropped  in  from  a  tap-funnel,  during  an  hour, 
through  the  top  of  the  condenser.  The  flask  is  then  heated  on  a  water 
bath  for  15  minutes,  its  contents  shaken  with  a  very  dilute  solution  of 
caustic  soda,  and  the  benzene  solution  separated.  The  aqueous  portion  is 
again  extracted  with  benzene,  and  the  whole  benzene  solution  dehydrated 
over  calcium  chloride,  the  benzene  removed  on  a  water  bath,  and  the 
residue  distilled  under  reduced  pressure,  the  fraction,  174° — 176°  at 
80  mms.,  being  retained. 

C6H5CH2C1  +  C6H6  +  (Al/Hg)  =  C6H5.CH2.C6H5  +  HC1  +  (Al/Hg). 

Yield. — 33%  theoretical  (14  gms.).  Properties  (see  p.  53).  (J.  C.  S., 
67,  826.) 

Reaction  VI.  (d)  Action  of  Anhydrous  Aluminium  Chloride  on  a 
Mixture  of  an  Aromatic  Hydrocarbon  and  a  Diazonium  Compound.  (B., 
26,  1994.) — The  solid  diazonium  salt  is  warmed  with  an  aromatic  hydro- 
carbon and  anhydrous  aluminium  chloride.  As  a  by-product,  the  chlor- 
derivative  of  the  hydrocarbon  is  formed.    The  reaction  proceeds  thus  :— 

C6H5.N2.C1  +  C6H6(A1C13)  =  C6H5.C6H5  +  N2  +  HC1.(A1C13). 

Diphenyl  can  also  be  obtained  from  diazobenzene  chloride  by  treatment 
with  stannous  chloride.    (J.  pr.,  [2],  40,  97.) 

2C6H5.N2.C1^C6H5.C6H5  +  2N2  +  Cl2. 
SnCl2  +  Cl2  ~>  SnCl4. 

See  also  Reaction  VIII. 

Reaction  VII.  (a)  Action  of  Sodium  on  Halogen  Compounds  (Wiirtz, 
Fittig,  and  Freund).  (A.,  131,  303.) — The  application  of  this  reaction  to 
the  synthesis  of  paraffins  by  Wiirtz  was  of  great  importance  to  chemical 
theory,  as  it  afforded  strong  evidence  of  the  chain  linking  of  carbon  atoms, 
and  enabled  the  structure  of  many  hydrocarbons  to  be  determined  by 
their  syntheses. 

Fittig  applied  the  reaction  to  aromatic  hydrocarbons.  In  this  latter 
case  a  second  side-chain  may  be  introduced  from  a  di-halogen  derivative, 
simultaneously  with  the  first  or  subsequently  in  a  second  reaction.  All 
the  possibilities  of  the  reaction  are  illustrated  in  the  synthesis  of  anthra- 


THE  LINKING  OF  CARBON  TO  CARBON 


59 


cene  hydride  and  phenanthrene  simultaneously  from  o-bromobenzyl 
bromide. 


CH9Br  Br 


C6H4<  +  4Na  +  ^>C6H4 

CH2 


Br  BrCH2 


C6H4X        /      +  4NaBr 


CH9Br  BrCIL 


CH2.CH2 

/  \ 

<\SII,  +  4Na       ^CeH,  =  C6H4  C6H4 

Br  Br  +  4NaBr 

The  reaction  does  not  occur  with  the  same  readiness  in  all  cases,  the 
yields  obtained  varying  greatly.  j9-Bromotoluene  gives  a  good  yield  of 
^-xylene,  the  ortho-compound  a  poor  yield  of  the  corresponding 
hydrocarbon,  whilst  the  meta-compound  gives  none  whatever.  If  the 
reaction  is  sluggish,  it  may  be  promoted  in  many  cases  by  raising  the 
temperature  or  by  adding  a  little  ethyl  acetate.  If  the  reaction  is  too 
vigorous,  on  the  other  hand,  an  indifferent  solvent,  e.g.,  toluene,  ether,  or 
-  ligroin,  is  added  to  moderate  it.  Since  the  discovery  of  the  Friedel-Crafts 
reaction  its  very  wide  and  varied  application  has  led  to  its  supplanting  the 
Fittig  method,  than  which  in  most  cases  it  gives  better  yields. 

Freund  applied  the  method  to  the  synthesis  of  cycloparamns.  From 
trimethylenedibromide,  trimethylene  was  prepared,  whilst  hexamethylene- 
dibromide  vielded  hexamethylene  in  a  similar  manner.  (M.,  3,  626  ; 
A.  Ch.,  [5],  14,  488.) 

CH2 

+2Na  =       /\         +  2NaBr. 


CH2Br  CH2  CH2 

In  the  Fittig  reaction  it  is  to  be  noted  that  bromo-  andiodo-compounds 
?  give  better  yields  than  chloro-compounds. 

Preparation  9. — Ethyl  Benzene.  (Phenylethan.) 

t  C6H5.C2H5.       C8H10.  106. 

30  gms.  (excess)  of  metallic  sodium  in  the  form  of  small  pieces  of  wire 
are  slowly  added  to  120  c.cs.  of  anhydrous  ether  prepared  from  commercial 
ether  as  described  on  p.  209.    The  ether  is  contained  in  a  round  flask 

tf  (1  litre)  which  when  the  evolution  of  hydrogen  has  ceased,  is  attached  to 
an  upright  condenser  and  immersed  in  a  vessel  of  ice-water.    A  mixture 

i  of  78  gms.  (2  mols.)  of  bromobenzene  and  70  gms.  (excess)  of  ethyl  bromide, 
both  carefully  dehydrated,  is  added  and  the  mixture  left  to  stand  over- 
night. The  liquid  is  then  decanted  from  the  sodium  bromide,  which  has  a 
blue  colour,  and  the  latter  washed  twice  with  dry  ether.  The  ether 
is  removed  on  a  water  bath,  and  the  residue  fractionated  from  a  small 

I  distilling  flask,  the  fraction  132° — 135°  being  collected  separately. 

C6H5Br  +  C2H$Br  +  2Na  =  C6H5.C2H5  +  2NaBr. 


60 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Yield.— 60%  theoretical  (30  gms.).  Colourless  liquid  ;  B.P.  134°  ; 
D.  2f  0-8664.    (A.,  131,  303.) 

Note.— The  residue  in  the  flask  contains  unaltered  sodium.  This  must 
be  destroyed  by  adding  the  residue  in  small  portions  to  alcohol,  and 
allowing  to  stand  till  all  action  ceases. 

Preparation  10. — Dibenzyl.  (1-2-Diphenylethan.) 

C6H5.CH2.CH2.C6H5.       C14H14.  182. 

12  gms.  (slightly  more  than  2  mols.)  of  sodium  wire  are  added  to  50  gms. 
(2  mols.)  of  benzyl  chloride,  the  whole  refluxed  on  a  water  bath  until  no 
further  change  takes  place,  extracted  with  dry  ether,  and  the  extract 
fractionated,  the  fraction  244° — 254°  being  retained,  and  recrystallised 
from  alcohol.  The  reaction  goes  best  in  the  absence  of  a  solvent,  but 
toluene  can  be  added  to  lower  the  refluxing  temperature. 

2C6H5CH2C1  +  2Na  =  C6H5.CH2.CH2.C6H5  +  2NaCl. 

Colourless  needles  ;  soluble  in  benzene  and  in  hot  alcohol ;  M.P. 
51°— 52° ;  B.P.  248°  ;  D.  g>  0-9752.    (A.,  121,  250  ;  137,  258.) 

Reaction  VII.  (b)  Action  of  Metals  other  than  Sodium  on  Iodo-com- 
pounds.  (B.,  34,  2176.) — This  reaction  can  be  applied  in  both  the  aliphatic 
and  aromatic  series.  In  the  latter,  chloro-  or  bromo -compounds  can  also 
be  used  if  nitro-groups  are  present  in  the  ortho-  or  ^ra-positions.  The 
reaction  is  carried  out  by  heating  the  iodo  compound  with  zinc  if  aliphatic, 
or  with  copper  if  aromatic,  to  a  high  temperature  in  a  sealed  tube.  In  this 
way  n-octane  (di-w-butyl)  has  been  obtained  from  w-primary-butyl  iodide, 
and  diphenyl  from  iodobenzene. 

2RI  +  2Cu  =  KR  +  Cu2I2. 

The  reaction  is  only  suited  for  the  preparation  of  symmetrical  com- 
pounds from  one  halogen  compound.  Attempts  to  prepare  unsymmetrical 
ones  by  using  two  halogen  compounds,  give  mixtures  difficult  to  separate, 
because  the  two  halogen  compounds  used  must  be  both  aromatic  or  both 
aliphatic,  and  hence  condense  with  themselves  under  the  same  conditions 
as  they  condense  with  one  another.  Fittig's  method  is  free  from  this 
drawback. 

Preparation  11. — Diphenyl.  (Phenylbenzene.) 

C6H5.C6H5.       C12H10.  154. 

20  gms.  (2  mols.)  of  iodobenzene  are  heated  with  20  gms.  (excess)  of 
copper  powder  for  3  hours  in  a  sealed  tube  (see  p.  38)  to  230°.  The 
contents  of  the  tube  are  extracted  with  ether,  and  the  filtered  extract 
fractionated,  the  ether  being  removed  on  a  water  bath  and  the  fraction, 
245° — 255°,  retained  and  recrystallised  from  alcohol. 

2C6H5I  +  2Cu  =  C6H5.C6H5  +  Cu2I2. 

Yield. — 80%  theoretical  (6  gms.).  Colourless  leaflets  ;  soluble  in  hot 
alcohol ;  M.P.  70°— 71°  ;  B.P.  254°  ;  D.  *2  0  9845.    (B.,  34,  2176.) 


THE  LINKING  OF  CARBON  TO  CARBON 


6] 


Reaction  VIII.  Action  of  certain  finely  divided  Metals  on  diazonium 
compounds  in  Alcohol  or  Acetic  Anhydride  Solution. — This  reaction  is 
limited  to  the  preparation  of  s-diaryl  compounds.  Copper,  zinc,  or  iron 
powder  may  be  used,  but  the  former  is,  on  the  whole,  the  most  satisfactory, 
especially  when  it  has  been  freshly  prepared  according  to  Gattermann's 
recipe.  As  with  other  "  finely  divided  metal  "  reactions  of  this  type, 
there  is  a  Sandmeyer  analogue,  but  except  in  the  case  of  nitro-compounds, 
the  reaction  then  for  the  most  part  takes  a  different  course  (see  Reaction 
CLXVL). 

The  reaction  proceeds  smoothly  in  aqueous  or  absolute  alcoholic,  or  in 
acetic  anhydride  solutions.  (B.,  23,  1226  ;  28,  2049.)  Its  exact  course 
has  not  been  worked  out,  but  it  may  be  formulated  as  follows  : — 

ENH2  ->  EN2S04H 

2EN2.S04H  +  Cu  ->  EE  +  2N2  +  CuS04  +  H2S04. 

Peepakation  12. — Diphenyl  (Phenylbenzene). 

C6H5.C6H5.       C12H10.  154. 

31  gms.  (2  mols.)  of  aniline  dissolved  in  150c.cs.  of  water  and  40  gms. 
(slight  excess)  of  concentrated  sulphuric  acid  are  diazotised  in  the  usual 
way  (see  p.  366)  with  23  gms.  (2  mols.)  of  sodium  nitrite  in  10% 
solution.  The  diazo  solution  is  treated  with  100  gms.  of  98%  alcohol,  and 
50  gms.  (excess)  of  copper  powder  (see  p.  504)  are  added  while  the 
whole  is  well  stirred  (see  p.  37).  A  vigorous  evolution  of  nitrogen 
occurs,  and  by  the  end  of  the  reaction  the  temperature  has  risen  to  30°  or 
40°.  The  stirring  is  continued  for  an  hour,  and  then  the  mixture  is  steam 
distilled.  The  distillate  at  first  consists  chiefly  of  alcohol  with  small 
amounts  of  an  oil  insoluble  in  water.  Small  portions  of  it  are  tested  from 
time  to  time  by  dilution  with  water.  When  a  solid  precipitate  is  thus 
obtained,  the  distillate  is  separately  collected  until  no  more  solid  comes 
over.  The  distillate  is  then  heated  to  71°  to  melt  the  solid  diphenyl ;  on 
cooling,  the  liquid  may  be  easily  poured  off.  The  product  is  almost  pure, 
but  may  be  recrystallised  from  alcohol. 

100  gms.  of  zinc  powder  may  be  used  instead  of  the  copper.  With  it 
the  best  results  are  obtained  by  adding,  first,  10  c.cs.  of  a  cold  saturated 
solution  of  copper  sulphate,  and  then  the  zinc  as  above.  Care  must  be 
taken  in  this  case  not  to  let  the  temperature  rise  above  30° — 40°.  Iron 
powder  can  also  be  employed. 

Yield. — In  each  case  25%  theoretical  (6  gms.).  Properties  (see  p.  60). 
(B.,  23,  1226  ;  28,  2049.) 

Diphenyl  can  also  be  obtained  from  diazobenzene  sulphate  by  treating 
it  with  warm  benzene  (B.,  26,  1997),  but  the  method  is  not  of  much  im- 
portance, except  in  so  far  as  it  illustrates  the  well-known  reactivity  of 
diazo-compounds. 

Reaction  IX.  (a)  Action  of  Magnesium  Alkyl  or  Aiyl  Halide  on  certain 
Alkyl  or  Aryl  Halides  in  the  presence  of  Absolute  Ether  (Grignard).  (C. 
1906,  II.,  748.)—  The  Grignard  reaction  has  perhaps  a  wider  application 
than  even  the  Friedel*  Crafts  or  the  diazo  reaction.    When  an  alkyl  or  aryl 


62 


SYSTEMATIC  ORGANIC  CHEMISTRY 


bromide  or  iodide  is  treated  with  magnesium  powder  in  presence  of 
absolute  ether,  a  magnesium  alkyl  or  aryl  halide  is  formed. 

Mg  +  EI  =  RMgl. 

The  substance  so  formed  can  be  treated  with  a  large  variety  of  reagents 
to  give  a  correspondingly  large  number  of  compounds,  provided  there  is 
no  moisture  present,  the  smallest  trace  of  which  completely  inhibits 
reaction.  There  are  various  theories  to  account  for  the  action  of  the 
ether  or  the  other  solvents  which  can  be  used  in  its  place.  These  will  be 
found  discussed  in  any  large  text-book  on  organic  chemistry. 

When  alkyl  halides  act  on  an  absolute  ethereal  solution  of  magnesium 
alkyl  or  aryl  halide,  hydrocarbons  are  formed. 

RMgl  +  UJ.  =  RRj  +  Mgl2. 

The  same  type  of  reaction  occurs  when  magnesium  acts  on  an  excess  of 
an  alkyl  or  aryl  halide  in  the  presence  of  absolute  ether.  n-Hexyl  bromide 
in  this  way  yields  n-dodecane. 

C6H13Br  +  Mg  =  C6H13.MgBr. 
C6H13.MgBr  +  C6H13Br  =  C12H26  +  MgBr2. 

Further  apnlications  of  the  Grignard  reaction  are  given  under  Reactions 
XIV.,  XXII.,  XXXIV.,  XLIIL,  LX. 

Reaction  IX.  (b)  Action  of  Heat  on  the  Compound  formed  by  treating 
Magnesium  Alkyl  or  Aryl  Halide  with  a  Ketone  in  absolute  Ethereal 
Solution  (Grignard).  (B.5  35,  2647.)— When  the  Grignard  reagent  is 
treated  with  a  ketone,  the  following  reaction  occurs  : — 

BRjCO  +  EnMgI  =  RB1!R11C.OMgI. 

This  latter  compound  when  treated  with  water  is  hydrolysed  to  a  ter- 
tiary alcohol  RRjRjjCOH.  If,  however,  the  anhydrous  reaction  mixture 
be  heated  for  a  long  time  on  the  water  bath,  an  olefine  is  formed  with  the 
splitting-off  of  magnesium  hydroxyiodide. 

CH3I  +  Mg  =  CH3.Mg.I. 

CH3.Mg.I.  +  C6H6.CO.CHs  =  (CeH6)(CH8)aC.O.Mg.I. 
CH3 

(C6H5)(CH3)Cl.O.Mg.I  =  (C6H5)(CH3).C  :  CH2  +  Mg(OH)I. 

Acetophenone  and  magnesium  methyl  iodide  yield  2-phenyl-l-propene. 
As  can  be  seen  from  the  equation  one  at  least  of  the  radicals  R,  R1?  R1]L, 
must  have  a  non-tertiary  carbon  linked  in  the  intermediate  compound  to 
the  "  hydroxy-magnesium-iodide  "  carbon. 

Preparation  13—  1.1-Diphenyl-methyl-ethylene. 

(C6H5)2C:CH.CH3.        C15H14.  194. 

The  Grignard  reagent  is  prepared  from  6  gms.  (2  mols.)  of  dry  mag- 
nesium, and  39  gms.  (2  mols.)  of  ethyl  iodide  (redistilled),  as  described 
in  Preparation  18,  120  c.cs.  of  anhydrous  ether  being  used.  23  gms.  (1 
mol.)  of  dry,  finely  divided  benzophenone  are  added,  the  flask  being  cooled 


THE  LINKING  OF  CARBON  TO  CARBON 


63 


if  the  reaction  becomes  too  vigorous.  The  mixture  is  then  heated  6  hours 
on  a  water  bath,  treated  with  dilute  acid,  extracted  with  ether,  the  ether 
removed  on  a  water  bath,  and  the  residue  fractionated  under  reduced 
pressure,  the  fraction  169° — 170°  at  18  mms.  being  separately  collected  and 
recrystallised  from  petroleum  ether. 

C2H5I  +  Mg-*C3H5.Mg.I. 
C2H5.Mg.I  +  (C6H5)2CO  ->  (C6H5)2C(OMgI)CH2CH3. 
(C6H5)2C(OMgI)CH2CH3-^(C6H5)2C-CH.CH3  +  Mg(OH)I. 

Colourless  crystals  ;  M.P.  52°  ;  B.P.  18  169°— 170°.    (B.,  35,  2647.) 

Reaction  IX.  (c)  Action  of  Dimethyl  Sulphate  on  Magnesium  Alkyl  or 
Aryl  Halide  (Grignard). — When  a  Grignard  compound  is  treated  with 
dimethyl  sulphate,  methylation  of  the  alkyl  or  aryl  group  takes  place,  the 
metal-halogen  residue  being  split  off.    (B.  36,  2116.) 

E.Mg.Br  +  (CH3)2S04  =  R.CH3  +  Br.Mg.(CH3)S04. 

Diethyl  sulphate  reacts  similarly.    (Am.  Soc,  44,  2621.) 
The  yields  are  good,  as  is  to  be  expected  from  the  components  of  the 
reaction. 

It  will  be  noted  that  in  the  Grignard  reactions  so  far  described,  only 
bromo-  or  iodo-compounds  are  mentioned.  Chlorine  compounds  do  not 
enter  so  readily  into  this  reaction  ;  to  induce  them  to  react  it  is  usually 
necessary  to  add  a  crystal  of  iodine  (B.,  38,  2759),  or  mercuric  chloride 
(C,  1907,  I.,  872),  or  a  previously  prepared  magnesium  solution  (B.,  38, 
1746  ;  C,  1907,  I,  455). 

By  the  method  above  outlined,  toluene  has  been  prepared  from  bromo- 
benzene,  and  ^-xylene  from  ^-bromotoluene. 

Prepakation  i4.— ^-Xylene  (1.4-Dimethylbenzene). 

CH./  ^>CH3.       C8H10.  106. 

The  Grignard  reagent  is  prepared,  as  in  Preparation  18,  by  heating  67 
gms.  (1  mol.)_p-bromotoluene,  10  gms.  (1  mol.)  of  dry  magnesium  and  200 
c.cs.  of  anhydrous  ether.  When  almost  all  the  magnesium  has  disappeared, 
a  solution  of  50  gms.  (1  mol.)  of  dimethyl  sulphate  (caution  !)  in  anhydrous 
ether  is  added.  A  vigorous  reaction  takes  place,  and  after  it  subsides,  the 
reaction  product  is  poured  on  to  ice.  The  ether  is  removed  by  distillation, 
and  the  residue  is  steam  distilled.  The  oil  is  separated  from  the  distillate 
and  fractionated,  the  fraction,  136° — 140°,  being  collected. 

CH3C6H4Br  ->  CH3C6H4MgBr  ->  CH3.C6H4.CH3. 

Yield. — 75%  theoretical  (40  gms.).  Colourless  oil ;  characteristic 
odour  ;  B.P.  138°  ;  D.  24°  0-869.    (B.,  36,  2116.) 

Owing  to  the  closeness  of  the  boiling  points  of  the  three  xylenes  they 
cannot  be  readily  separated  one  from  the  others  ;  so  that  a  method  such 
as  the  above,  by  which  one  isomer  can  be  obtained  free  from  the  others,  in 
a  good  yield,  is  of  importance.  For  some  details  on  magnesium  aryl 
halides  see  B.,  36,  2898. 


64 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Note. — Dimethyl  sulphate  is  extremely  poisonous  ;  on  no  account  must 
its  vapour  be  inhaled.    All  work  with  it  should  be  carried  out  in  a  good 
fume  cupboard  ;  it  must  be  added  to  mixtures  by  means  of  a  tap-funnel,  i 
for  if  spilled  on  the  hands  it  is  readily  absorbed  through  the  skin.  Should 
any  fall  on  the  clothes,  they  must  be  changed  at  once. 

Reaction  X.  Action  of  Zinc  Aikyl  on  Alkyl  Halides. — The  action  of 
zinc  alkyl  on  various  types  of  compounds  is  much  the  same  as  that  of 
magnesium  alkyl  or  aryl  halide.  Before  the  discovery  of  the  latter,  zinc 
alkyl  was  widely  used  as  a  general  synthetic  reagent,  but  its  spontaneous 
inflammability  led  to  its  replacement  by  the  more  conveniently  prepared 
Grignard  reagent ;  it  does  not  form  aryl  compounds  ;  even  in  alkyl 
syntheses  it  is  not  nearly  so  widely  applicable,  its  one  advantage  being  that  4 
the  reactions  it  does  bring  about  go  somewhat  more  smoothly  than  the 
corresponding  magnesium  reactions. 

Zn(CH3)2  +  2CH3I  =  Znl2  +  2C2H6. 


CHAPTER  IV 


carbon  to  carbon 

Hydroxy  Compounds 

The  condensations  now  to  be  considered  include  all  those  in  which  the 
reaction  is  such  that  there  is  of  necessity  a  hydroxyl  group  in  the  final 
product. 

Reaction  XI.  Intramolecular  Elimination  of  Water  from  certain  Mole- 
cules. (A.,  227,  242.) — When  phenyl  isocrotonic  acid  is  heated,  water  is 
eliminated  and  a-naphthol  is  formed.  This  synthesis  which  is  of  theo- 
retical interest,  was  discovered  by  Fittig.  It  is  one  of  the  proofs  of  the 
structure  of  naphthalene. 


CH  CH 


Reaction  XII.   Reduction  of  Aldehydes  and  Ketones  to  Pinacones. 

(B.,  27,  456.) — When  ketones  are  reduced  to  secondary  alcohols,  some 
intermolecular  condensation  usually  also  occurs,  and  a  pinacone  is  formed. 

2RR1CO  +  2H  =  RR1C(OH).C(OH).RR1. 

This  side  reaction  cannot  be  avoided  when  reducing  aliphatic  ketones, 
but  in  the  aromatic  series  either  product  can  be  obtained  by  varying  the 
conditions  of  the  reduction.  An  alkaline  reduction  favours  ketone  pro- 
duction ;  pinacones  are  formed  when  acid  reducing  agents  are  employed 
(see  Preparation  15). 

Pinacones  can  also  be  obtained  by  using  suitable  electrolytic  reductions. 
Aldehydes,  too,  have  been  brought  within  the  scope  of  the  reaction.  Thus 
hydrobenzoin  (s-diphenyl-ethan-diol)  has  been  prepared  from  benzalde- 
hyde  by  an  acid  reduction. 

2C6H5.CHO  ->  C6H5.CH(OH).CH(OH).C6H5. 

Acetone,  the  simplest  ketone,  gives  the  simplest  pinacone. 

2(CH3)2CO  ->  (CH3)2C(OH)C(OH)(CH3)2. 

The  pinacones  formed  from  acetophenone,  benzophenone,  and  many 
s.o.c.  65  r 


66 


SYSTEMATIC  OKGANIC  CHEMISTEY 


other  ketones  are  exactly  similar  in  structure  (C,  1906,  II.,  148 ; 
B.,  27,  454  ;  G,  1900,  II.,  794  ;  C.,  1903,  II.,  23). 
Preparation  15— Benzpinacone  (s-Diphenyl-ethan-diol). 

(C6H5)2.C(OH).C(OH).(C6H5)2.       C26H2202.  366. 

5  gms.  (2  mols.)  of  benzophenone  are  boiled  for  J  hour  with  50  gms.  of 
85%  acetic  acid  and  10  gms.  of  zinc  foil,  the  whole  being  well  shaken 
throughout.  The  liquid  is  decanted  from  the  zinc  residues,  cooled,  and 
filtered  ;  the  filtrate  is  again  boiled  up  with  zinc,  and  this  process  repeated 
a  third  time,  the  same  filter  being  used  each  time.  The  benzpinacone 
remaining  on  the  filter  is  then  washed  with  85%  acetic  acid,  and 
recrystallised  from  13  parts  of  boiling  glacial  acetic  acid. 

2(C6H5)2CO  +  H2  =  (C6H5)2C(OH).C(OH)(C6H5)2. 

Yield  —  90%  theoretical  (4-5  gms.).  Colourless  crystals  ;  M.P.  (with 
decomposition)  168°.    (C,  1881,  150  ;  A.,  133,  26  ;  B.,  10,  1473.) 

For  the  "  pinacoline  transformation  "  undergone  by  pinacones,  see  p.  74. 

Reaction  XIII.  Condensation  of  a  Phenol  with  Formaldehyde  (Lederer- 
Manasse).  (B.,  27,  2411.)— This  reaction  can  take  three  different  courses 
according  to  conditions. 

(i.)  With  the  more  powerful  condensing  agents,  e.g.,  caustic  alkalis  or 
hydrochloric  acid,  a  diphenyl  methane  compound  is  usually  formed. 

2C6H5OH  +  H.CHO  =  HO.C6H5.CH2.C6H4OH  +  H20. 

(ii.)  The  less  powerful  condensing  agents,  e.g.,  alkali  carbonates, 
alkaline  earth  oxides,  lead  oxide,  or  dilute  acids  or  alkalis,  give  a  benzyl 
alcohol  or  sometimes  a  di-(hydroxy-methyl)  compound. 

C6H5OH  +  H.CHO  =  OH.C6H4.CH2OH 
C6H4(CH3)(OH)[l  :  4]  +  2H.CHO  =  C6H2(CH3)(OH)(CH2OH)2[l  :  4  :  3  :  5]. 

(lii.)  Hydrochloric  acid  sometimes  gives  a  benzyl  chloride  derivative, 
the  benzyl  alcohol  first  formed  being  chlorinated  by  the  acid.  Such 
chlorides  are  easily  hydrolysed  to  the  alcohol  (see  Preparation  124). 

0HC6H4.C1[1  :  2]  +  H.CHO  ->  C6H3(OH)(Cl)(CH2OH)[l  :  2  :  4] 
~>  C6H3(0H)(C1)(CH2C1)[1  :  2  :  4]. 

In  all  three  cases  the  ^ara-position  to  the  hydroxyl  group  is  preferred  ; 
if  it  is  occupied,  condensation  takes  place,  but  less  readily,  in  the  ortho-. 
The  above  rules  as  to  which  condensation  a  given  reagent  will  bring  about 
are  only  general,  in  no  particular  case  can  it  be  foretold  with  certainty  how 
far  the  reaction  will  go. 

The  reaction  is  of  importance,  especially  when  as  in  (ii.)  it  is  used  for  the 
production  of  phenolic  methanols.  Lately  formaldehyde  has  been  con- 
densed at  higher  temperatures  with  phenol  to  give  substances  resembling 
celluloid,  and  articles  made  from  this  synthetic  celluloid  are  now  on  the 
market  (Bakelite,  etc.). 

For  other  formaldehyde  condensations,  see  Keactions  XIX.  (6), 
XXXIIL  (a),  XLV. 


CARBON  TO  CARBON 


07 


Pkeparation  16. — o-  and  j9-Hydroxybenzyl  Alcohols  (1:2-  and  1 :  4- 
Methylolhydroxybenzene). 

C6H4.(OH)(CH2OH).       CvH802.  124. 

30  gms.  (1  mol.)  of  phenol  are  dissolved  in  150  c.c.  (a  slight  excess)  of 
10%  caustic  soda  ;  35  gms.  (excess)  of  40%  formaldehyde  solution  are 
added,  and  the  whole  allowed  to  remain  at  room  temperature  for  6  days. 
It  is  neutralised  with  hydrochloric  acid,  extracted  repeatedly  with  ether, 
and  the  latter  removed  on  a  water  bath.  If  necessary  the  residue  is 
steam-distilled  to  remove  unchanged  phenol,  and  the  benzyl  alcohols 
which  are  left  are  then  shaken  for  some  time  with  cold  benzene  until 
nothing  further  dissolves.  The  or^o-compound  which  is  much  the  more 
soluble,  is  thus  separated  from  the  para-. 

C6H5(OH)  +  H.CHO  =  OH.C6H4.CH2OH. 

Yield. — Including  both  compounds  80%  theoretical  (32  gms.). 
o-Hydroxybenzyl  alcohol  (saligenin)  forms  colourless  crystals  ;  M.P. 
82°  ;  the  ^ara-compound  melts  at  112°.    (B.,  27,  2411.) 

Preparation  17. — 3  :  5  :  3'  :  5'-Tetramethyl-2-2'-Dihydroxy-Diphenyl- 
methane  (Di-(3  :  5-Dimethyl-2-Hydroxyphenyl-(l) ) -Methane). 


CH, 


CH3 

/\ 

CH 

/\ 

-CH2  

OH 

C17H20O2.  256. 


10  gms.  (2  mols.)  of  xylenol  (1  :  3-dimethyl-4-hydroxybenzene)  are  dis- 
solved in  300  c.cs.  (excess)  of  1-5%  caustic  soda  solution ;  5  gms.  (excess) 
of  40%  formaldehyde  solution  are  added,  and  the  mixture  allowed  to 
stand  for  4  days.  It  is  then  acidified  with  acetic  acid  and  extracted  with 
ether,  the  solvent  removed  on  a  water  bath,  and  the  residual  oil  left  in  a 
vacuum  over  sulphuric  acid  until  at  length  it  becomes  almost  a  solid. 
The  latter  is  recrystallised  several  times  from  ligroin. 

2C6H3(CH3)2(OH)[l  :  3  :  4]  +  CH20  =  [3:5:  6]C6H2(CH3)2(OH).CH2.C8Ha— 
(CH3)2(OH)[3-  :  5':  6']  +  H20. 

Long  colourless  needles  ;  easily  soluble  in  alcohol,  ether,  chloroform, 
acetic  acid,  benzene  ;  sparingly  soluble  in  cold  ligroin  ;  M.P.  145° — 146°  ; 
when  boiled  for  1  hour  with  acetic  anhydride  a  diacetate  is  obtained  which, 
when  recrystallised  from  dilute  alcohol,  forms  fine  needles,  M.P.  86°. 
(B.,  40  ;  2526.) 

Reaction  XIV.  (a)  Action  of  Magnesium  Alkyl  or  Aryl  Halide  on  Alde- 
hydes and  Ketones  (Grignard).  (B.,  31,  1003.)— This  phase  of  the  Grig- 
nard  reaction  can  be  utilised  for  the  preparation  of  all  types  of  alcohols 
(C,  1901,  L,  725  ;  II,  622  ;  1902,  I,  414). 

(i.)  Primary  alcohols  can  be  obtained  from  formaldehyde,  or  rather 
from  its  polymer  trioxymethylene,  which  has  to  be  used  in  place  of  the 
usual  aqueous  solution.    Magnesium  phenyl  iodide  and  trioxymethylene 

F  2 


68 


SYSTEMATIC  ORGANIC  CHEMISTRY 


yield  benzyl  alcohol  for  example,  the  usual  Grignard  intermediate  com- 
pound being  formed. 

C6H5MgI  +  CH20  ->  H2C(C6H5)OMgI  ->  C6H5CH2OH. 

(ii.)  Other  aldehydes  yield  in  the  same  way  secondary  alcohols. 
Acetaldehyde  and  methyl  iodide  give  isopropyl  alcohol. 


CH3CHO  +  MgCH3I 


(CH3)C(CH3)OMgI 


(CH3)2CHOH. 


Benzaldehyde  and  magnesium  phenyl  bromide  or  iodide  give  diphenyl 
carbinol. 

C6H5CHO  +  MgC6H5I  ->  (C6H5)2CHOMgI  ->  (C6H5)2CHOH. 

(C.  r.,  130,  1322  ;  B.,  31,  1003). 

(hi.)  Tertiary  alcohols  are  formed  from  ketones. 

The  simplest  tertiary  alcohol  is  prepared  from  acetone  and  magnesium 
methyl  iodide. 

Mg(CH3)I  +  (CH3)2CO  ->  (CH3)2C(CH3)OMgl  ->  (CH3)3C(OH). 

Methyl  ethyl  ketone  and  methyl  iodide  give  tertiary  amyl  alcohol. 

CH3COC2H5  +  CH3MgI  =  (CH3)2.COH.C2H5  +  Mg(OH)I. 

Coming  to  the  aromatic  series,  acetophenone  and  methyl  iodide,  for 
example,  yield  phenyldimethyl  carbinol.  An  important  step  in  the 
synthesis  of  'i-terpineol  is  the  preparation  of  ethyl-S-hydroxy-hexahydro 
jo-toluate  from  ethyl-S-ketohexahydrobenzoate  and  magnesium  methyl 
iodide. 


CO 


H9C 


CH, 


CIL 


C(CH3)OH. 

H,C  /\  CH2 


+  MgCH3I  =  HaC 


CH, 


HC 


CH 


COOEt. 


COOEt. 
+  Mg(OH)I. 


The  usual  precautions  must  be  taken  in  all  these  reactions,  to  guard 
against  the  possibility  of  moisture  being  present.  The  technique  of  the 
method  will  be  apparent  from  the  following. 

Preparation  18.— (1)  Phenylmethyl  Carbinol  (l-Phenyl-ethanol-(l) ). 

HC(CH3)(C6H5)OH.       C8H10O.  122. 
All  reagents  used  must  be  thoroughly  dry. 

(1.)  36  gms.  (1  mol.)  of  methyl  iodide  which  have  been  allowed  to  stand 
for  12  hours  over  calcium  chloride  and  then  redistilled,  are  mixed  with 
50  c.cs.  of  ether  purified  and  dried  as  described  on  p.  209.  20  c.cs. 
of  this  mixture  are  run  into  a  flask  fitted  with  a  dropping  funnel  and  long 
reflux  condenser.  The  flask  contains  6  gms.  (1  mol.)  of  magnesium  ribbon, 
which  has  been  cleaned  with  emery  paper  and  dried  in  the  air  oven  at 


CARBON  TO  CARBON 


69 


110° — 1:20°  for  several  hours.  If  necessary,  the  reaction  is  started  by 
adding  a  crystal  of  iodine.  When  the  first  reaction  has  subsided,  70  c.cs. 
of  dry  ether  are  added,  and  the  remainder  of  the  mixture  of  alkyl  iodide 
and  ether  run  in  drop  by  drop  from  the  tap-funnel.  The  contents  of  the 
flask  are  then  boiled  on  the  water  bath  until  all  (or  nearly  all)  of  the 
magnesium  has  dissolved. 

(2.)  The  flask  is  now  disconnected,  and  under  cooling  by  ice- water, 
26  gms.  (1  mol.)  of  freshly  distilled  benzaldehyde  mixed  with  an  equal 
volume  of  dry  ether  are  dropped  in  from  a  tap-funnel  with  constant 
shaking,  and  the  whole  allowed  to  stand  for  12  hours. 

(3.)  Just  sufficient  hydrochloric  acid  to  dissolve  the  precipitate  is  added 
with  constant  shaking  and  cooling.  The  aqueous  layer  is  separated,  and 
the  ether  washed  first  with  sodium  bicarbonate  solution,  then  with  sodium 
bisulphite  (to  remove  free  iodine)  and  again  with  sodium  bicarbonate. 
The  extract  is  dried  over  potassium  carbonate  and  the  ether  removed  on 
a  water  bath.  The  carbinol  which  remains  is  fractionated  under  reduced 
pressure. 

(1)  CH3I  +  Mg  =  CHaMgL 

(2)  C6H5CHO  +  CH3MgI  =  C6H5(CH3)CH(OMgI). 

(3)  (C6H5)(CH3)CH(OMgI)  +  H20  =  (C6H5)(CH3)CHOH  +  (OH)Mgl. 

Yield. — 56%  theoretical  (20  gms.).  Colourless  liquid  ;  insoluble  in 
water  ;  B.P.  15  100°  ;  B.P.  28  110°— 111°  ;  B.P.  10  118°  ;  B.P.  760  203°  ; 
D.  \5  1-013.    (C.  r.,  130,  1322  ;  B.,  31,  1003.) 

The  same  method  may  be  used  for  phenylethyl  carbinol  taking  39  gms. 
(1  mol.)  of  ethyl  iodide.  The  compound  is  obtained  as  a  colourless  liquid  ; 
B.P.760  221°  ;  D.1!  0-9900. 

Peeparation  19. — Tertiary  Butyl  Alcohol  (2-Methyl-2-propanol). 

(CH3)3C(OH).       C4H10O.  74. 

The  Grignard  compound  is  prepared  as  described  in  Preparation  18  from 
36  gms.  (1  mol.)  of  dry  methyl  iodide,  120  c.c.  of  sodium-dried  ether,  and 
6  gms.  (1  mol.)  of  dry  magnesium  ribbon  or  powder.  14  gms.  (1  mol.)  of 
dry  acetone  dissolved  in  30  c.c.  of  dry  ether  are  slowly  added  from  a  tap 
funnel  with  constant  shaking  and  under  cooling  by  ice-water.  A  white 
bulky  precipitate  of  the  magnesium  compound  separates.  After  standing 
overnight,  just  sufficient  dilute  sulphuric  acid  to  dissolve  the  precipitate 
is  added  with  constant  shaking  and  cooling.  The  ether  solution  of  the 
alcohol  separates  and  is  withdrawn  and  distilled. 

(CH3)2CO  +  Mg.CH3.I  =  (CH8)aC(CH8).OMgI. 
(CH3)3C(OMgI)  +  H20  =  (CH3)3C(OH)  +  Mg(OH)I. 

Colourless  crystals  ;  soluble  in  water  ;  M.P.  25°  ;  B.P.  83°  ;  D.  34°  0-7788. 

In  an  exactly  similar  manner,  using  39  gms.  (1  mol.)  of  ethyl  iodide, 
dimethylethyl  carbinol  may  be  prepared.  It  is  obtained  as  a  colourless 
liquid,  soluble  in  water  ;  B.P.762  102°  ;  D.1*  0-8144. 

The  following  shows  the  method  of  preparing  and  using  magnesium  aryl 
halides  in  this  synthesis. 


I 


70  SYSTEMATIC  OBGANIC  CHEMISTRY 

Preparation  20. — Triphenyl  Carbinol  (Triphenylmethanol). 

(C6H5)3C(OH).       C19H160.  260. 

1-2  gms.  (1  mol.)  of  bright  magnesium  ribbon  is  dried  in  the  air  oven  at 
110°,  cut  into  1  cm.  pieces,  and  treated  in  a  well-dried  round-bottomed 
300-c.c.  flask  with  a  solution  of  8  gms.  (1  mol.)  of  bromobenzene  in  40  gms. 
of  sodium-dried  ether  to  which  a  crystal  of  iodine  has  been  added.  The 
flask  is  now  warmed  on  a  water  bath,  under  a  reflux  condenser  in  a  current 
of  dry  hydrogen  (caution  !  no  flame  must  approach  the  end  of  the  con- 
denser.) Light  flocculse  appear  in  the  liquid  ;  they  are  due  to  unavoidable 
moisture,  but  they  soon  disappear,  and  then  the  magnesium  begins  to 
dissolve.  When  the  magnesium  has  completely  dissolved,  except  for 
traces  of  impurities — this  should  not  take  more  than  2  hours — the  heating 
is  stopped,  and  the  liquid  is  treated  at  ordinary  temperatures  with  9-1  gms. 
(1  mol.)  of  benzophenone  dissolved  in  25  gms.  of  sodium-dried  ether.  The 
liquid  becomes  red,  then  a  thick  tough  precipitate  separates,  which,  when 
the  heating  is  renewed,  reacts  vigorously,  and  solidifies  in  the  course  of  half 
an  hour.  The  reaction  mixture  is  then  allowed  to  cool,  and  treated  with 
pieces  of  ice  and  sulphuric  acid.  When  decomposition  is  complete,  steam 
is  passed  through  until  the  distillate  is  clear.  This  removes  ether  and  all 
by-products  (benzene,  diphenyl)  ;  almost  pure  triphenyl  carbinol  remains, 
and  is  recrystallised  from  benzene. 

C6H5.Br  +  Mg  =  C6H5.Mg.Br. 
C6H5.MgBr  +  C6H5.CO.C6H5  =  (C6H5)2C(C6H5)OMgBr. 
(C6H5)2C(C6H5)(OMgBr)  +  H20  =  (C6H5)3C.OH  +  OH.Mg.Br. 

Yield. — 75%  theoretical  (10  gms.).  Colourless  crystals  ;  soluble  in 
ether  and  hot  benzene  ;  gives  a  deep  red  solution  in  strong  sulphuric  acid  ; 
in  glacial  acetic  acid  it  is  colourless,  but  addition  of  a  drop  of  concentrated 
hydrochloric  acid  gives  a  deep  yellow  coloration  ;  M.P.  159°. 

Diphenylmethyl  carbinol  is  prepared  in  the  same  way  from  6  gms.  of 
acetophenone. 

Reaction  XIV.  (b)  Action  of  Magnesium  Alkyl  or  Aryl  Halide  on  Esters, 
Acyl  Chlorides,  and  Acid  Anhydrides.  (C,  1901,  I.,  725  ;  II.,  622  ;  1902, 

I.,  1414.) — In  all  the  above  cases  tertiary  alcohols  are  obtained,  except,  of 
course,  in  the  case  of  formic  esters  when  secondary  alcohols  are  formed. 
Using  esters  the  reaction  has  a  wide  application,  as  the  examples 
given  below  show  ;  the  use  of  the  acyl  chlorides  and  anhydrides  is  only 
of  theoretical  interest.  The  reactions  in  all  cases  take  the  usual 
"  Grignard  "  course. 

RCO.OEt  +  2MgR1Br  — >■  EC.OMgBr  +  Mg(OEt)Br. 

K 

R(B,1)2C(OH)  +  OH.MgBr. 
RC(R1)2OMgBr  +  MgBr.Cl. 
R(R1)2C.OH  +  Mg(OH)Br. 
2R(R1)2C.OMgBr  +  0(MgBr)2. 
-  2R(R1)2COH. 


RCfR^OMgBr  +  H20  -> 
RCO.C1  +  2MgRjBr  -> 
RfR^aOMgBr  +  H20  = 
(RCO)20  +  4MgR!Br  = 
2R(R1)2COMgBr  — ; 


CARBON  TO  CARBON 


71 


The  yields  are  in  most  cases  good,  and  the  reactions  smooth.  A  great 
advantage  of  the  Grignard  reaction  is  that  it  can  be  applied  to  complicated 
derivatives  of  the  reacting  substances.  This  renders  it  valuable  in  the 
synthesis  of  substances  such  as,  e.g.,  terpenes.  The  following  list  should 
give  some  idea  of  the  scope  of  the  reaction. 

(i.)  Ethyl  formate  and  magnesium  ethyl  iodide  give  diethyl  carbinol. 

(ii.)  Methyl  acetate  and  magnesium  methyl  iodide  give  tertiary  butyl 
alcohol  (cf.  Reaction  XIV.  (a)  (iii.) ). 

(iii.)  Ethyl  A'-tetrahydro-jo-toluate,  see  p.  68,  and  magnesium 
methyl  iodide  give  i-terpineol  (l-(2-methyl-2-ethylol)-4-methyl-3-cyclo- 
hexene). 

(iv.)  Ethyl  chloracetate  and  magnesium  phenyl  bromide  give  diphenyl- 
chlorhydrin. 

(v.)  Methyl  benzoate  and  magnesium  phenyl  bromide  give  triphenyl 
carbinol. 

(vi.)  Acetyl  chloride  and  magnesium  methyl  iodide  give  trimethyl 
carbinol. 

(vii.)  Acetic  anhydride  and  magnesium  ethyl  iodide  give  diethylmethyl 
carbinol. 

The  equations  of  the  above  reactions  should  be  written  out.  An 
interesting  application  of  the  method  such  as  contained  in  (iii.)  should 
be  looked  up  first-hand  in  the  literature. 

It  may  be  mentioned  that  the  "  Grignard  "  reaction  can  also  be  applied 
to  the  production  of  primary  alcohols  by  the  interaction  of  ethylene  oxide 
and  magnesium  alkyl  halide.    (C,  1907,  I.,  1102  ;  1908,  II.,  105.) 

CH2  CH2— OMgBr  CH2 — OH 

^>0  +MgBrC2H5->    |                       ->  | 
CH2  CH2 — CH2 — CH3        CH2  CH2 — CH3. 

Preparation  21. — Triphenyl  Carbinol  (Triphenylmethanol). 

(C6H5)3C(OH).       C19H160.  260. 

The  Grignard  reagent — magnesium  phenyl  bromide — is  prepared  as 
described  in  Preparation  20  from  1-2  gms.  (1  mol.)  of  dry  magnesium  and 
8  gms.  (1  mol.)  of  dry  bromobenzene.  6-8  gms.  (1  mol.)  of  dry  methyl 
benzoate  dissolved  in  25  gms.  of  sodium-dried  ether  are  added  to  the  cold 
solution,  slowly,  and  with  constant  shaking.  The  liquid  is  then  heated  on 
a  water  bath  until  no  further  change  takes  place.  Ice  and  dilute  sulphuric 
acid  are  added  to  the  cold  reaction  mixture,  which,  when  the  precipitate 
has  dissolved,  is  steam-distilled.  The  triphenyl  carbinol  which  remains  is 
recrystallised  from  benzene. 

C6H5COOCH3  +  2C6H5MgBr  ->  (C6H5)3C.O.MgBr  ->  (C6H5)3C(OH). 
See  p.  70. 

Reaction  XV.  Action  of  Zinc  Alkyl  on  Aldehydes,  on  certain  Ketones, 
and  on  Acyl  Chlorides.  (A.,  223,  162.)— As  with  other  "  zinc  alkyl " 
reactions  the  corresponding  Grignard  reaction  described  in  Reaction  XIV. 


72 


SYSTEMATIC  ORGANIC  CHEMISTRY 


lias  replaced  it  almost  completely,  so  that  the  following  is  only  of  more  or 
less  historical  and  theoretical  interest. 

(a)  With  all  aldehydes  except  formaldehyde,  secondary  alcohols  are 
formed  (A.,  213,  369  ;  B.,  14,  2557). 

H20 

CH3CHO       (CH3)2CHOZnCH3   >  (CH3)2CHOH. 

This  reaction  only  occurs  with  zinc  methyl  and  zinc  ethyl ;  with  the 
higher  zinc  alkyls  the  aldehydes  are  reduced  to  the  corresponding  alcohols 
(B.,  17,  R.,  318  ;  A.,  223,  162). 

(b)  In  general  ketones  do  not  react  with  zinc  alkyl.  Exceptions  are 
certain  ketones  which  do  not  contain  a  methyl  group  attached  to  the 
carbonyl  group,  e.g.,  diethyl  ketone,  ethylpropyl  ketone.  These  with 
zinc  methyl  or  ethyl  yield  the  usual  zinc-oxy-alkyl  compounds  which, 
treated  with  water,  give  tertiary  alcohols  (B.,  19,  60  ;  21,  R.,  55). 

H20 

(C2H5)2CO  ->  (C2H5)3COZnC2H5   >  (C2H5)3C(OH). 

(c)  With  acid  chlorides  the  reaction  takes  place  in  three  stages  (Z.  ch., 
1864,  385  ;  1865,  614). 

(i.)  One  molecule  of  the  zinc  alkyl  reacts  and  the  usual  type  of  addition 
compound  is  formed. 

CI. 

/ 

CH3COCl  +  Zn(CH3)2  ->  (CH3)2COZnCH3. 
If  water  be  now  added,  a  ketone  is  obtained. 

(ii.)  If  a  second  molecule  of  the  zinc  alkyl  act  upon  the  new  com- 
pound, another  reaction  takes  place. 

(CH3)2C(Cl)(OZnCH3)  +  Zn(CH3)2  ->  (CH3)3COZnCH3  +  Zn(CH3)(Cl). 

(iii.)  Addition  of  water  yields  now  a  tertiary  alcohol. 

H20 

(CH3)3C(O.Zn.CH3)   >  (CH3)3C(OH). 

If  in  the  second  stage  another  zinc  alkyl  be  used,  tertiary  alcohols  con- 
taining two  or  three  different  alkyl  groups  can  be  prepared  (A.,  175,  374  ; 
188,  110,  122  ;  C,  1910,  II.,  1201).  Only  zinc  methyl  and  zinc  ethyl  thus 
furnish  tertiary  alcohols  ;  zinc  propyl  produces  only  those  of  the  secondary 
type  (B.,  16,  2284  ;  24,  R.,  667).  The  historical  importance  of  the  acid 
chloride  method  lies  in  the  fact  that  in  1864  it  led  to  the  discovery  of 
tertiary  alcohols. 

Reaction  XVI.  Action  of  certain  Oxidising  Agents  on  a-  and  ^-Naph- 
thols.  (J.  R.  C.  S.,  6,  183.) — If  to  an  aqueous  solution  of  a  naphthol  a 
few  drops  of  a  neutral  aqueous  solution  of  ferric  chloride  be  added,  a  green 
coloration  is  produced,  and  after  a  time,  a  flocculent  precipitate  of 
dinaphthol.  Performed  in  this  way  on  the  "  test-tube  "  scale,  the  xeaetion 
is  very  useful  for  identification  purposes. 


CARBON  TO  CARBON 
-]iihy<3 


73 


Pkepakation  22. — a-a-Dinaphthol  (^'-Dihydroxydinaphthyl). 

OH  OH 


C20H14O2.  286. 


10  gms.  (2  mols.)  of  a-naphthol  are  dissolved  in  the  minimum  quantity 
of  boilin^bater,  and  ferric  chloride  solution  is  gradually  added  on  cooling, 
until  the  precipitate  formed  is  a  bright  reddish- violet.  The  latter  is 
filtered  off,  and  is  boiled  once  with  water,  and  twice  with  benzene.  The 
residue  is  recrystallised  from  alcohol. 

2C10H7OH.  +  0  =  OH.C10H6.C10H6.OH  +  H20. 

Yield. — 35 — 40%  theoretical  (7 — 8  gms.).  Shining  rhombic  crystals  ; 
insoluble  in  water  ;  soluble  in  alcohol  and  ether  ;  slightly  soluble  in 
chloroform  and  benzene  ;  M.P.  300°.    (J.  R.  C.  S.,  6,  183.) 

A  solution  of  a-naphthol  in  very  dilute  alcohol  can  also  be  used  in  the 
above  preparation. 

Preparation    23. — /3-j6-Dinaphthol  (o-o'-Dihydroxy-m-m'-dinaphthyl) , 


OH  HO 


C20H14O2.  286. 


10  gms.  (2  mols.)  of  /3-naphthol  are  dissolved  in  an  excess  of  ether, 
and  16  gms.  (excess)  of  anhydrous  ferric  chloride  are  gradually  added  to 
the  solution  in  a  flask  fitted  with  a  reflux  condenser.  Much  heat  is 
evolved  during  this  operation.  The  mixture  is  then  refluxed  on  a  water 
bath  until  most  of  the  naphthol  is  oxidised.  (To  test  this  a  small  portion 
of  the  ethereal  solution  is  treated  with  an  excess  of  dilute  hydrochloric  acid, 
and  the  ether  evaporated.  The  dinaphthol  separates  out  even  in  the 
warm  as  an  oil  while  /3-naphthol  crystallises  out  on  cooling.)  When  this 
is  the  case,  the  ether  is  removed  on  a  water  bath,  water  and  powdered 
calcium  carbonate  are  added  to  the  residue,  and  the  whole  well  shaken. 
Excess  caustic  soda  is  then  added,  the  solution  is  filtered,  and  precipitated 
with  dilute  sulphuric  acid.  The  precipitate  is  washed  with  boiling  water 
or  boiling  ligroin,  and  recrystallised  from  benzene. 

2C10H7OH  +  2FeCl3  =  OH.C10H6.C10H6.OH  +  2FeCl2  +  2HC1. 

Yield. — 40%  theoretical  (8  gms.).  Colourless  needles  from  alcohol, 
prisms  from  a  mixture  of  carbon  disulphide  and  alcohol ;  insoluble  in 
water  ;  slightly  soluble  in  chloroform  ;  soluble  in  alcohol  and  ether  ; 
M.P.  216°  ;  M.P.  (corr.)  218°  ;  Forms  a  picrate.  (J.  R.  C.  S.,  6,  187  ; 
B.,  15,  2166.) 


CHAPTER  V 


carbon  to  carbon 
Oxy  Compounds 

In  the  following  section  are  discussed  the  more  important  of  those  con- 
densations which  give  rise  to  oxy  compounds — aldehydes,  ketones,  and 
quinones.  The  reactions  in  this  section,  as  in  all,  may  be  divided  into 
two  classes — those  in  which  the  product  is  an  oxy  compound,  because  oxy 
compounds  only  undergo  the  reaction — the  oxy  group  playing,  so  to  speak, 
a  catalytic  part,  e.g.,  Reaction  XX.  (6) ;  and  those  in  which  an  oxy  com- 
pound is  actually  formed  during  the  action  from  non-oxy  starting  sub- 
stances, e.g.  Reaction  XVII. 

Owing  to  the  peculiar  activating  properties  of  the  oxy  group,  the  former 
class  looms  large  in  the  following,  more  so  than  in  the  reactions  discussed 
in  the  previous  section. 

Reaction  XVII.  Intramolecular  rearrangement  of  the  Glycols  (Pinacoline 
Transformation).  (B.,  36,  2016.) — Di-primary,  primary-secondary,  pri- 
mary-tertiary, and  di-secondary  glycols  yield  aldehydes  by  withdrawal  of 
water  and  rearrangement,  when  heated  with  hydrochloric  or  sulphuric 
acids,  or  with  certain  dehydrating  agents.  Ethylene  oxide  derivatives 
may  be  considered  to  be  intermediate  compounds,  for  the  ethylene  oxide 
compounds  themselves  undergo  the  same  change. 

Hydrobenzoin  yields  diphenylacetaldehyde. 

C6H5.CH(OH).CH(OH).C6H5  — >  C6H5.CH.CH.C6H5  ->  (C6H5)2.CH.CHO. 


0 

(C,  1907,  I,  15  ;  B.,  36,  2016  ;  C,  1905,  II.,  237.) 

Secondary-tertiary  and  di-tertiary  glycols  change  into  ketones  in  the 
same  way,  similar  elimination  of  water  and  migration  of  an  alkyl  group 
occurring. 

The  di-tertiary  glycols — known  as  "  pinacones  " — undergo  this  reaction 
with  great  readiness,  yielding  ketones — ■"  pinacolines."  The  simplest  of 
the  di-tertiary  glycols  is  tetramethyl  glycol  or  pinacone,  and  this,  by  the 
transformation,  gives  pinacoline.  (C,  1906,  II.,  670.) 

(CH3)2:C(OH)  (CH3)2:C 

I  i/° 
(CH3)2  :  C(OH)  (CH3)2  :  CT 

->  (CH3)3C.CO.CH3 

The  reaction  itself  is  called  the  "  pinacoline  transformation."  Ethers 
of  the  glycols  also  behave  similarly,  in  some  cases  with  particular  ease 

74 


CARBON  TO  CARBON 


75 


(B.,  39,  2288  ;  A.,  Ch.,  [8],  9,  484).  For  a  corresponding  reaction  among 
ketones,  see  p.  105. 

Reaction  XVIII.  Ring  Formation  by  Elimination  of  Water  from  certain 
Molecules.  (B.,  41,  3632  ;  A.,  311,  178.)— Many  important  syntheses  of 
ring  compounds  come  under  this  heading.    Only  a  few  can  be  mentioned. 

(i.)  1  :  2-Diketones  containing  a  CH2  group  together  with  the  CO  group 
can  be  condensed  to  quinone  derivatives — -diacetyl,  for  example,  readily 
yields  dimethyl  quinone — under  the  action  of  alkalis,  ketols  are  inter- 
mediately formed. 

CH3.COCO.CH3  CH8C(OH).CO.CHs 

CH3.CO.CO.CH3  CH2.CO.CO.CH3 
CH3C(OH)CO.CH2  CH3C.CO.CH 

I  I  ">  II  II 

CH2CO.   0(OH)CH3  CH.CO.C.CH3. 

(B.,  22,  2215  ;  28,  1845.) 

(ii.)  The  o-benzoylbenzoic  acids  give  anthraquinone  derivatives  on 
heating  with  dehydrating  agents.    This  synthesis  is  very  similar  to  that 
of  a-naphthol  from  phenyl-^o-crotonic  acid  (Reaction  XI.),  but  there 
is  no  rearrangement  of  the  primary  product.  (Z.,  a  Ch.,  19,  669.) 
COx  CO 


H 

:  ! 

C6H4  i  'fC6H4  ->  C6H4/  yC6H, 


o-Benzoylbenzoic  acid  (Reaction  XXXV.  (a) )  itself  yields  anthraquinone, 
and  2-j9-toluoylbenzoic  acid  gives  2-methyl-anthraquinone.  These  syn- 
theses are,  at  present,  mostly  of  theoretical  interest  in  throwing  light  on 
the  structure  of  anthraquinone  and  hence  of  anthracene,  but  there  is  some 
probability  of  their  becoming  industrially  important  (see  Reaction  XX. 
(a),  also  Preparation  24). 

(iii.)  When  ethylidene  bisacetoacetic  ester  is  refluxed  with  cone, 
sulphuric  acid,  simultaneous  condensation  to  a  ring  compound,  hydrolysis, 
and  elimination  of  carbon  dioxide  take  place,  and  a  cyclic  ketone  is  ob- 
tained. All  compounds  which,  like  ethylidene  bisacetoacetic  ester,  contain 
1  :  5-carbonyl  groups,  and  in  addition  a  methyl  group  attached  to  one  of 
them,  undergo  the  same  condensation  with  acids  or  alkalis,  so  that  there 
exists  here  a  very  general  method  of  passing  from  open-chain  to  ring  com- 
pounds.   To  take  the  most  general  case— 

X-CH-CO  X-CH-CO 


H2CH       ->  R<CH  V)H 

RCH  \  / 


\  0 
Y — CH — C— Z 


Y—CH— C— Z 


76 


SYSTEMATIC  ORGANIC  CHEMISTRY 


In  the  example  given  above- 


C2H5OOC — CH — CO 


C2H5OOC  CH-CO  /  I 

/         \  '  (H 

/  H„CH 


(CH3)CH 
C2H5OOC— CH— CO— CH. 


(CH3)CH  C.CH3. 


C2H5OOC.CH 


A  further  reaction  then  takes  place  in  this  particular  instance  (see  the 
Preparation),  but  in  the  general  case  the  reaction  goes  no  further.  The 
compounds  so  obtained  are  all  derivatives  of  cyclo-hex-l-en-3-on.  These 
latter  compounds  may  be  transformed  by  various  reactions  into  cyclo- 
parafhns  on  the  one  hand,  and  aromatic  compounds  on  the  other.  This 
affords  a  method  of  passing  from  simple  aliphatic  to  aromatic  compounds 
(see  Preparation  445).    (A.,  281,  25.) 

(iv.)  The  last  example  is  the  final  step  in  the  all  but  successful  attempt 
of  Tiemann  and  Kriiger  to  synthesise  the  natural  perfume  "  irone  " — the 
odiferous  principle  of  the  iris  root  and  also,  probably,  of  the  violet.  Having 
obtained  a  pseudo-ionone  (Reaction  XXIV.  (ii.)  ),  these  two  chemists 
treated  it  with  sulphuric  acid  and  obtained  two  ring  compounds,  a-  and 
/Monone — each  an  isomeride  of  irone  (B.,  26,  2675). 

C(CH3)2 :  CH.CH2.CH2C(CH3) :  CH.CH  :  CHCOCH3 
C(CH3)2 


H2C/       \CH.CH  :  CH.CO.CH. 

H2cl  JC(CH3) 

CH 
a-  Ionone 
C(CH3)2 


and  H2C/       \C.CH  :  CH.CO.CH3 

H2d  Jc(CH3) 


CH2 


3-Ionone. 

These  compounds  have  an  odour  of  violets,  and  are  used  in  the  manu- 
facture of  violet  essence.    Irone  itself  has  the  formula — 


HC 
HC 


C(CH3)2 

\CH.CH  :  CH.CO.CH. 
/JcH(CH3) 
CH2 


CARBON  TO  CARBON 


77 


Preparation  24. — Anthraquinone. 

/CCk 


C.H 


>C6H4       C14H802.  208. 


10  gins.  (1  mol.)  of  o-benzoylbenzoic  acid  are  mixed  with  60  gms.  of 
cone,  sulphuric  acid,  heated  to  150°  for  1  hour,  cooled  and  poured  on  to 
ice.  The  precipitated  anthraquinone  is  collected  and  thoroughly  washed, 
first  with  hot  water  then  with  warm  dilute  (5N)  caustic  soda  and  finally 
with  warm  water.  It  is  dried  in  a  steam  oven,  and  completely  purified 
by  sublimation,  at  250°  (see  p.  28). 

CO  CO 


\/  \ 


:H 


CO;  OH 


CO 


Yield. — Theoretical  (9  gms.).  Yellow  needles  ;  insoluble  in  water  ; 
somewhat  soluble  in  benzene  and  the  usual  organic  solvents  ;  soluble  in 
glacial  acetic  acid  ;  M.P.  277°  ;  sublimes  at  250°  ;  B.P.  382°.  (Z.  a.,  19, 
669.) 

In  the  above  preparation  phosphorus  pentoxide  can  equally  well  be  used 
instead  of  sulphuric  acid. 

2-Methyl  anthraquinone  can  be  prepared  by  heating  2-£>-toluoyl- 
benzoic  acid  with  about  9  times  its  weight  of  oleum  containing  20% 
S03.  On  dilution  with  water,  and  re  crystallising  from  dilute  acetic  acid, 
pale  yellow  needles  are  obtained,  M.P.  177°.  (B.,  41,  3632;  J.  pr.  [ii], 
33,  318;  A,,  311,  178). 

Preparation  25. — Dimethylcyclohexenone  (l-3-Dimethyl-5-on-6-cyclo- 
hexen). 


CH,CH 


CH2 

CO 

A  

CH2 

C.CH3 

CJL,0. 


124. 


Crude  ethylidinebisacetoacetic  ester  as  prepared  in  Preparation  72  is 
melted  on  the  water  bath  and  poured  into  500  c.cs.  20%  sulphuric  acid  in 
a  round-bottomed  flask  attached  to  a  reflux  condenser.  A  few  pieces  of 
porcelain  chips  are  added,  and  the  whole  vigorously  boiled  for  7  hours.  It 
is  then  steam  distilled  until  the  distillate  measures  about  100  c.cs.  The 
distillate  is  then  set  aside  for  24  hours  in  a  well-stoppered  bottle.  The 
residue  is  again  refluxed  for  7  hours  and  again  steam  distilled,  100  c.cs.  of 
distillate  being  again  collected.  The  process  is  repeated  a  third  time,  and 
then  steam  is  blown  into  the  mixture  until  no  oil,  or  only  a  trace,  separates 
from  a  test  portion  when  treated  with  solid  caustic  potash.    To  the  three 


78 


SYSTEMATIC  ORGANIC  CHEMISTRY 


united  distillates  is  now  added  pure  anhydrous  solid  caustic  potash  until 
the  solution  is  saturated.  A  reddish-brown  oil  separates,  and  is  removed 
by  means  of  a  separating  funnel.  The  alcohol  is  distilled  off  using  a 
column,  and  the  residue  dried  over  anhydrous  sodium  sulphate.  The 
dimethylcyclohexenone  is  then  recovered  from  the  residue  by  fractional 
distillation,  the  fraction  200° — 215°  being  retained. 

C2H5OOCCH — CO 


C2H5OOC.CH — CO 

/  I 
/  CH3 
CH3CH 

C,H,OOC— CH— COCH. 


/ 

CH,CH 


C2H5OOCC 


CC!H- 


2C02  +  2C2H5OH  +  CH3CH 


CH 


CH, 


\ 
CH 

/ 

-C.CH 

-CO\ 


\CH,~- 


CH 

/ 

-C.CH. 


Yield— 75— 90%  theoretical  (15—18  gms.).  Colourless  liquid,  B.P. 
211°.    (A.,  281,  25.) 

Reaction  XIX.  (a)  Condensation  of  Anthranol  Derivatives  with 
Glycerol.  (B.,  44,  1666.)— This  condensation  gives  rise  to  the  benz- 
anthrones  which  are  used  as  intermediates  in  the  dye  industry.  The 
reaction  may  be  assumed  to  go  as  follows — 


CHOH 

/ 

/ 

/ 

\  ! 
> 

H2COH; 

HO;  . 

CH.i 

/   V  "  \ 

Hi 

H2C^ 
C 


CH 


CH 


C(OH) 


CH 


C(OH) 


/\  / 


HC  /       xx  CH 
C 


CO 


CARBON  TO  CARBON 


79 


1  Sulphuric  acid  is  the  condensing  agent  used.  The  reaction  might  be 
compared  with  the  preceding  reaction  and  with  Skraup's  quinoline 
synthesis  (see  p.  159). 


Preparation  26.— Benzanthrone. 

C     =  CoH, 


C6H4X       \C6H3      C17H10O.  230. 


CO 

10  gms.  (1  mol.)  of  anthranol  are  dissolved  or  suspended  in  150  gms.  of 
sulphuric  acid  (80%),  and  10  gms.  (excess)  of  glycerol  are  added.  The 
mixture  is  carefully  heated  to  120°,  when  S02  is  evolved,  and  kept  there 
till  the  reaction  is  complete  (4  hours).  The  cooled  mass  is  poured  into 
water,  and  the  product  which  separates  is  collected,  washed,  boiled  for 
30  minutes  with  13  times  the  quantity  of  1%  sodium  hydroxide  solution, 
pressed  and  dried.    It  is  recrystallised  from  alcohol. 

/C(0H)X  !  ' 


C,H,^  )>CeH4  +  C3H5(0H)3       C6H4/  \C6H, 


N-CU-/  CO 

Pale  yellow  needles  ;  insoluble  in  cold  alcohol  and  in  dilute  acids  and 
alkalis  ;  soluble  in  cone,  sulphuric  acid  with  a  reddish-brown  colour,  and 
deep  orange  fluorescence  ;  M.P.  170°.  (D.R.P.  176018  ;  see  also  B.,  44, 
1666.) 

Reaction  XIX.  (b)  Condensation  of  Anthranol  Derivatives  with 
Formaldehyde.  (A.,  420,  134.) — The  anthranols  can  also  give  rise  to  other 
intermediates  by  condensation  with  formaldehyde.  Methylene  anthra- 
quinone  is  thus  obtained  from  anthranol. 


CH. 

+  CH20 


C(.OH) 

Reaction  XX.  (a)  Action  of  Metallic  Zinc  on  a  Mixture  of  an  Aromatic 
Hydrocarbon  and  a  Derivative  of  Phthalyl  Chloride. — This  is  a  method  of 
synthesising  anthraquinone  and  its  derivatives,  and  hence  a  method  of 
elucidating  their  structure,  and  also  the  structure  of  anthracene.  Other- 
wise the  method  is  not  of  importance,  but  it  may  be  in  the  future,  since 
anthraquinone  is  in  great  and  increasing  demand  for  the  production 
of  the  new  vat-dyes,  such  as  indanthrene  ;  phthalyl  chloride  can  be 


80 


SYSTEMATIC  ORGANIC  CHEMISTRY 


obtained  cheaply  from  naphthalene  (see  also  Reaction  XVIII.  (ii.),  and 
p.  115). 

CO 

.  CO  .  CI 

+ 

.  CO  .  CI 


The  action  of  zinc  in  this  case  resembles  that  of  anhydrous  aluminium 
chloride  in  the  Friedel-Craft  reaction.  If  the  structure  of  anthraquinone 
is  accepted,  this  reaction  helps  to  support  the  formula  of  phthalyl  chloride 
as  given  above  against  the  alternative  formula. 


\-CO 

> 

y  CC12 


for  which  there  is  also  evidence  (A.,  238,  329  ;  see  Reaction  XX.  (6)  (vi.)  ). 

Reaction  XX.  (6)  Action  of  certain  Anhydrous  Metallic  Halides 
(Aluminium  Chloride,  Aluminium  Bromide,  Aluminium  and  Hydrogen 
Chloride,  Ferric  Chloride)  on  a  mixture  of  an  Aromatic  Hydrocarbon  or 
certain  derivatives,  and  an  Acyl  Halide.  (Friedel-Crafts).  (A.  Ch.,  [6],  1, 
518.) — This  is  an  even  more  important  application  of  the  Friedel-Crafts 
synthesis  than  the  methods  of  synthesising  hydrocarbons  (pp.  54,  56). 
The  reactions  involved  are  more  readily  controlled  since  the  products,  in 
presence  of  aluminium  chloride,  do  not  undergo  further  condensations. 
Usually  these  products  have  also  the  advantage  of  being  more  easily 
separated,  for  as  shown  below  in  (hi.),  the  formation  of  isomers  can  be 
avoided. 

What  has  been  said  under  Reaction  VI.  covers  the  general  experi- 
mental methods  of  the  synthesis,  the  same  solvents  and  considerations 
applying  in  all  cases.  The  following  will  give  some  idea  of  the  scope  of 
the  reaction. 

(i.)  Both  aliphatic  and  aromatic  acyl  chlorides  can  be  used  (A.  Ch.,  [6], 
1,  503  ;  14,  455). 

C6H6  +  CHgCOCl  =  C6H5.CO.CH3  +  HC1. 
C6H6  +  C6H5C0C1  =  C6H5.CO.C6H5  +  HC1. 

(ii.)  Homologues  of  both  the  reacting  substances  may  be  employed. 

C6H6  +  CH3CH2COCl  =  C6H5.CO.CH2.CH3  +  HC1. 
C6H6  +  C6H5CH2C0C1  =  C6H5.CO.CH2.C6H5  +  HC1. 
C6H5CH3  +  C6H5C0C1  =  p-CH3C6H4COC6H5  +  HC1. 

(A.,  189,  84  ;  B.,  12,  2299.) 

(iii.)  The  acid  radical  always  enters  the  joara-position  to  the  alkyl 
radical ;  if  that  is  occupied,  it  goes  to  the  ortho-.  A  little  of  the  ortho- 
compound  is  formed  along  with  the  para-  in  all  cases,  so  that  in  preparing, 


CARBON  TO  CARBON  81 

for  instance,  phenyl-jo-tolyl-ketone,  the  method  given  in  the  last  equation 
should  not  be  used,  but  it  should  be  made  from  benzene  and  £>-toluoyl 
chloride,  when  it  is  the  only  compound  formed.  (A.,  189,  84  ;  B.,  12,  2299.) 

C6H6  +  ^-CH3C6H4C0C1  =  jp-CH8C6H4COC6H5  +  HCL 

The  pure  o-  and  m-compounds  can  be  prepared  in  a  similar  manner, 
(iv.)  Instead  of  the  hydrocarbons  the  phenol  ethers  which  react  with 
great  ease  can  be  employed  ;  the  same  rules  as  to  position  apply. 

C6H5.O.CH3  +  C6H5.C0.C1  =  ^-CH3O.C6H4.COC6H5  +  HCL 

(v.)  Substituted  acid  chlorides  may  be  used  to  obtain  substituted 
ketones. 

C6H6  +  ^-Br.C6H4.COCl  =  p-BrC6H4COC6H5  +  HCL 
C6H6  +  i?-N02C6H4COCl  =  ^)-N02C6H4COC6H5  +  HC1. 

(vi.)  The  chlorides  of  the  dibasic  acids  react  in  two  ways  :  (a)  With 
1  mol.  of  hydrocarbon  they  give  acid  chlorides,  (b)  With  2  mols.  of 
hydrocarbon  di-ketones  are  formed,  except  in  the  case  of  phosgene. 

COCl2  +  2C6H6  =  CO.(C6H5)2  +  2HC1. 
(B.,  10,  1854.) 

C0C12  +  2C6H5CH3  =  CO.(C6H4.CH3)2[4  :  4']  +  2HC1. 
(A.,  312,  92  ;  B.,  7,  1183  ;  10,  2173  ;  J.  pr.,  [2],  35,  466.) 

C0C12  +  C6H5N(CH3)2  =  CO(C6H4N(CH3)2)2[4  :  4']  +  2HC1. 

(B.,  19,  109  ;  B.,  24,  3198.) 

The  last  compound  4  :  4/-tetramethyl-di-amino-benzophenone  is  also 
known  as  "  Michler's  ketone,"  and  is  an  important  intermediate  in  the 
preparation  of  dyestuffs  of  the  fuchsine  series,  e.g.,  crystal  violet.  As  to 
di-ketones,  the  following  examples  will  suffice — 

CH2 .  CO  .  CI  CH2.CO.C6H5 

+  2C6H6  =  |  +  2HC1. 

CH2 .  CO  .  CI  CH2.CO.C6H5 


(B.,  13,  320.) 


C6H5 

C^2  J  C*H 

\  /  C  \ 


C6H4/  )0  +  2  C6H6  =  C6H4/  \Q 

\co/  \co/ 

00       +  2HC1 

With  phthalyl  chloride  "  diphenylphthalide,"  important  on  account 
of  its  relation  to  the  fluorescein  dyes,  is  formed  (B.,  14,  1865). 

Comparing  with'  Reaction  XX.  (a)  it  will  be  seen  that  phthalyl  chloride 
is  probably  tautomeric.  Succinyl  chloride  is  also  considered  to  be  simi- 
larly tautomeric,  a  number  of  facts  supporting  this  view.  Unlike  phthalyl 
chloride,  however,  it  reacts  symmetrically,  as  has  been  seen,  with  benzene 
and  aluminium  chloride. 


82 


SYSTEMATIC  ORGANIC  CHEMISTRY 


(vii.)  Naphthalene  reacts  in  a  manner  similar  to  benzene. 

C10H8  +  C6H5C0C1  =  «-C10H7COC6H5  +  HC1. 

It  will  be  noted  in  the  following  examples  that  the  quantities  of  alu- 
minium chloride  used  are  larger  than  in  the  case  of  the  hydrocarbons 
synthesised  by  this  reaction.  This  is  necessary  owing  to  the  stability  of 
the  addition  compounds  aluminium  chloride  forms  with  the  product.  So 
stable  are  these  compounds  that  the  aluminium  chloride  is  unable  to 
exert  its  catalytic  action,  and  molecular  quantities  of  the  condensing 
agent  have  to  be  taken.    (J.  C.  S.,  83,  1470.) 

Preparation  27 .— Acetophenone  (l-Phenyl-l=Ethanon). 

C6H5.CO.CH3.       C8H80.  120. 

50  gms.  (1  mol.)  of  freshly  prepared  finely  powdered  anhydrous  alu- 
minium chloride  (see  p.  503)  are  placed  in  a  500-c.c.  flask  attached  to 
an  upright  condenser,  30  gms.  (1  mol.)  of  dry  benzene  are  immediately 
added,  and  then,  while  cooling  the  flask  by  ice-water,  35  gms.  (excess) 
of  acetyl  chloride  are  slowly  dropped  in  from  a  tap-funnel  fitted  to  the 
top  of  the  condenser.  A  brown  viscid  mass  is  formed  which,  after  standing 
for  1  hour,  is  poured  on  to  ice  and  extracted  with  a  little  benzene.  The 
extract  is  washed  with  dilute  caustic  soda  and  with  water,  dehydrated 
over  calcium  chloride,  filtered  and  distilled.  The  fraction  190° — 205°  is 
redistilled. 

C6H6  +  CHgCOCl  +  AICI3   =  C6H6C0CH3[A1C13]  +  HC1. 
C6H6C0CH3[A1C13]  +  3H20  =  C6H6COCH3  +  Al(OH)3  +  3HC1. 

Yield. — 50%  theoretical  (20  gms.).  Colourless  plates  ;  sweetish  odour  ; 
insoluble  in  water  ;  soluble  in  benzene  ;  M.P.  20°  ;  B.P.  202°  ;  D.  J  1-032. 
(A.  Ch.,  [6],  1,  507  ;  14,  455.) 

Note. — In  all  these  experiments  the  aluminium  chloride  must  be  weighed 
out  in  a  dry  test-tube  closed  by  a  cork. 

Preparation  28. — Benzophenone  (Diphenyl-methanon). 

C6H5.CO.C6H5.       C13H10O.  182. 

30  gms.  (excess)  of  dry  benzene,  30  gms.  (1  mol.)  of  pure  benzoyl  chloride, 
and  130  gms.  of  dry  carbon  disulphide  are  placed  in  a  dr}^  flask  and  29 
gms.  (1  mol.)  of  freshly  prepared,  finely  powdered,  anhydrous  aluminium 
chloride  are  added. 

The  flask  is  then  connected  with  a  long  reflux  condenser,  and  heated  on 
a  water  bath  kept  at  50°,  until  only  small  amounts  of  hydrogen  chloride 
are  evolved  (about  2  J  hours).  The  carbon  disulphide  is  then  distilled  off  on 
a  water  bath  (caution)  and  the  still  warm  residue  is  carefully  poured  into 
a  large  flask  containing  300  c.cs.  of  ice-water.  The  reaction  flask  is  then 
washed  out  into  the  ice-water  flask  with  100  c.cs.  of  wa'ter,  10  c.cs.  of  cone, 
hydrochloric  acid  are  added,  and  the  whole  steam  distilled  for  15  minutes. 
The  cold  residue  is  extracted  with  ether,  the  ethereal  solution  is  repeatedly 
washed  with  water,  filtered,  and  three  times  washed  with  dilute  caustic 
soda  solution.    It  is  dehydrated  over  calcium  chloride,  filtered  and 


CARBON  TO  CARBON 


83 


distilled  from  a  "high  boiling  point"  distilling  flask  (see  p.  18),  the 
fraction  209°— 305°  being  retained. 

C6H6  +  C6H5C0C1  +  A1C13  =  CeH6.CO.C6H6[AlCl8]  +  HC1. 
C6H5C0C6H5[A1C13]  +  3H20  =  C6H5.CO.C6H5  +  Al(OH)8  +  3HC1. 

Yield. — 80%  theoretical  (30  gms.).  Colourless  crystals  ;  insoluble  in 
water  ;  soluble  in  benzene  ;  M.P.  48°  ;  B.P.  763  297°  ;  B.P.  12  162°  ; 
a  labile  modification  (M.P.  26°)  also  exists  ;  it  transforms  to  the  stable 
modification  on  boiling  or  on  touching  with  a  little  of  the  latter.  (B.,  26, 
R.,  380  ;  A.  Ch.,  [6],  1,  518.) 

The  effect  of  carbon  disulphide  on  the  velocity  of  the  action,  and  on 
the  yield  should  be  noted  by  comparing  the  above  preparation  with  the 
preceding. 

Preparation  29. — Acetylmesitylene  (1:3:  5  -  Tri-methyl  -  2-acetyl  - 
benzene). 

.  CH3 

\cOCH3       CnH140  162. 


CH 


CH, 


25  gms.  (1  mol.)  of  mesitylene  (see  p.  53),  75  gms.  of  carbon  disul- 
phide and  30  gms.  (excess)  of  freshly  distilled  acetyl  chloride  are  placed 
in  a  flask  provided  with  a  reflux  condenser,  and  33  gms.  mols.)  of 
finely  powdered,  freshly  prepared,  anhydrous  aluminium  chloride  are 
added,  gradually.  The  mixture  is  finally  warmed  for  15  minutes  on  a 
water  bath  and  poured  on  to  ice,  10  c.cs.  of  cone,  hydrochloric  acid  are 
added,  and  the  whole  is  steam-distilled  until  no  more  oily  drops  pass  overt 
The  distillate  is  extracted  with  benzene  and  the  extract  washed  with 
dilute  caustic  soda  solution  and  with  water,  dried  over  calcium  chloride 
and  distilled,  the  fraction  230° — 240°  being  retained. 

C6H3(CH3)3[1  :  3  :  5]  +  CH3.CO.Cl  =  C6H2(CH3)3(CO.CH3)[l  :  3  :  5  :  2]  -f  HC1. 

Yield.— 60%  theoretical  (36  gms.).  Colourless  liquid  ;  B.P.  235°.  (B.. 
24,  3542.) 

Preparation  30. — p-p' -Dimethyl  Benzophenone. 

[4']CH8.C6H4.CO.C6H4CH8[4'].       C15H140.  210. 

This  preparation  must  be  conducted  in  a  good  draught  cupboard. 

100  gms.  of  toluene,  containing  20%  of  carbonyl  chloride  (see  p.  509),  are 
placed  in  a  flask  to  which  is  attached  by  a  two-holed  stopper  a  reflux  con- 
denser and  a  wide-stemmed  glass  filtering  funnel.  To  the  end  of  the  con- 
denser is  attached  a  delivery  tube  leading  to  a  fume  duct.  The  flask  is 
surrounded  by  a  freezing  mixture,  and  50  gms.  of  finely  powdered  anhy- 
drous aluminium  chloride  are  gradually  added  through  the  funnel  during 
4  hours,  the  funnel  being  closed  by  a  cork  after  each  addition.  When  all 
has  been  added,  the  flask  is  very  gently  warmed  for  a  short  time,  and  the 
contents  slowly  poured  into  ice-water  (caution).    It  is  then  steam- 

g  2 


84 


SYSTEMATIC  ORGANIC  CHEMISTRY 


distilled  until  nothing  further  passes  over.  The  aqueous  layer  of  the 
distillate  is  removed  and  a  1%  solution  of  hydrochloric  acid  added  to  the 
solid  matter,  which  is  again  steam-distilled  for  about  30  minutes. 

The  solid  matter  in  the  distillate  is  filtered  off,  washed  and  recrystallised 
several  times  from  dilute  alcohol. 

2C6H5CH3  +  COCl2-^CO(C6H4.CH3[4])2  +  2HC1. 

Yield. — 50%  theoretical  (22  gms.).  Colourless  needles  ;  insoluble  in 
water  ;  soluble  in  benzene  and  alcohol ;  M.P.  95°  ;  B.P.  333°.  (B.,  10, 
2173  ;  A.,  312,  92  ;  J.  pr„  [2],  35,  466.) 

Note. — Carbonyl  chloride  is  extremely  poisonous,  and  special  care  must 
be  taken  in  its  use. 

Reaction  XX.  (c)  Action  of  a  Mixture  of  Aluminium  and  Mercuric 
Chloride  on  a  Mixture  of  an  Aromatic  Hydrocarbon  and  an  Alkyl  Halide. 
(J.  C.  S.,  117,  1330.) — This  modification  of  the  Friedel-Crafts  condensation 
has  been  fully  dealt  with  under  its  application  to  the  synthesis  of  hydro- 
carbons. In  the  case  of  ketones  the  results  obtained  are  more  in  accord- 
ance with  the  results  of  the  older  method  than  were  those  discussed  in  the 
first  hydrocarbon  section. 

Pkeparation  31. — Acetophenone  (1 -Phenyl- 1-ethanon). 

C6H5.CO.CH3.       C8H80.  120. 

20  gms.  (1  mol.)  of  dry  benzene,  and  20  gms.  of  mercuric  chloride  are 
placed  in  a  flask  fitted  with  a  reflux  condenser  and  1  gm.  of  aluminium 
powder  is  added,  gradually,  and  with  vigorous  shaking,  the  ensuing  reaction 
being  moderated  by  occasional  cooling  in  an  ice  bath.  A  green,  crystal- 
line mass  separates,  and  the  reaction  is  completed  by  immersing  the  flask 
in  tepid  water  for  half  an  hour.  The  mercury  liberated  in  the  reaction  is 
removed  and  the  preparation  of  the  catalyst  is  complete.  20  gms.  (1  mol.) 
of  acetyl  chloride  are  added  in  small  quantities  through  the  condenser,  the 
reaction  mixture  being  well  agitated  by  a  mechanical  stirrer.  (For  a 
suitable  apparatus,  see  Fig.  37.)  The  whole  is  allowed  to  stand  for  2 
hours,  and  then  heated  to  40°  for  1  hour.  ,On  cooling,  water  is  added  to 
decompose  the  product,  and  the  liberated  oil  extracted  with  benzene.  The 
extract  is  dried  over  calcium  chloride  and  fractionated,  the  fraction  195° — 
205°  being  retained. 

C6H6  +  Al  +  2HgCl2  =  C6H6.AlCl3.HgCl  +  Hg. 
C6H6.AlCl3.HgCl  +  CHgCOCl  =  CH3.CO.C6H5.AlCl3.HgCl  +  HC1. 
2CH3COC6H5.AlCl3.HgCl  +  6H20  =  2CH3COC6H5  +  2A1(0H)3  + 

Hg2Cl2  +  6HC1. 

Yield. — 60%  theoretical  (18  gms.).  Colourless  plates  ;  sweetish  odour  ; 
soluble  in  benzene  ;  insoluble  in  water  ;  M.P.  20°  ;  B.P.  202°  ;  D.  \  1-032. 
(J.  C.  S.,  117,  1330.) 

The  yield  of  acetophenone  above  is  10%  better  than  that  obtained  in 
the  ordinary  Friedel-Crafts  reaction.  A  similar  method  can  be  applied  to 
the  preparation  of  ^>-tolyl-methyl-ketone,  20  gms.  (1  mol.)  of  dry  toluene, 
2  gms.  of  aluminium  powder,  35  gms.  of  mercuric  chloride,  and  17  gms. 
(1  mol.)  of  acetyl  chloride  being  used.  The  yield  is  45%  theoretical 
(13  gms.).    The  ketone  is  obtained  as  a  low-melting  solid,  B.P.  224°. 


CARBON  TO  CARBON 


85 


Reaction  XX.  (d)  Combined  Action  of  Carbon  Monoxide  and  Hydrogen 
Chloride  on  an  Aromatic  Hydrocarbon  in  presence  of  a  Mixture  of  Anhy- 
drous Aluminium  and  Cuprous  Chlorides  (Gattermann-Koch).  (B.,  30, 
1622  ;  31,  1149  ;  A.,  347,  347.)— When  it  was  discovered  that  a  mixture 
of  carbon  monoxide  and  hydrogen  chloride  behaved  as  the  unknown 
formyl  chloride,  it  became  possible  to  utilise  directly  the  Friedel-Crafts 
method  in  the  synthesis  of  aldehydes. 

The  reaction  may  be  expressed  by  the  following  equations — 

HC1  +  CO[Cu2Cl2]  =  H.CO.Cl.[CuaCl2]. 
CH3.C6H5  +  H.C0.C1[A1C18]  =  CH8.C6H4.CHO.rAl.Cl3]  +  HC1. 
CH3.C6H4.CH0.[A1C13]  +  3H20  =  CH3.C6H4.CHO  +  Al(OH)3  +  3HC1. 

Benzene  itself  does  not  react — unless  hydrobromic  acid  is  used — and 
can  on  that  account  be  used  as  a  solvent  (D.R.P.,  126421). 

Many  other  hydrocarbons  o-  and  m-xylene,  mesitylene,  ethylbenzene, 
diphenyl,  etc.,  can  all  be  employed  to  give  the  corresponding  aldehydes. 
The  CHO  group  enters  the  jwa-position  to  the  alkyl  residue  just  as  in  the 
ketonic  synthesis.    Thus  o-xylene  gives  3  :  4-di-methyl-benzaldehyde. 

Since  the  Friedel-Crafts  reaction  when  applied  to  the  phenol  ethers 
yields  the  corresponding  ketones  far  more  easily  than  the  same  reaction 
applied  to  hydrocarbons  (see  Reaction  XX.  (b)  (iv.)  ),  it  is  noteworthy 
|  that  the  above  reaction  does  not  apply  to  the  phenol  ethers.  To  obtain 
aldehydes  from  them  or  from  phenols,  a  modified  method  must  be  used 
(see  p.  100). 

Preparation  32. — ^-Tolylaldehyde  (1-4-Methylbenzaldehyde). 

CH3.C6H4.CHO[l  :  4].       C8H80.  120. 

To  30  gms.  (1  mol.)  of  freshly  distilled  toluene  (B.P.  110°)  contained  in 
a  wide-necked  vessel  cooled  with  water,  45  gms.  of  pulverised,  freshly 
prepared  aluminium  chloride  and  5  gms.  of  pure  cuprous  chloride  are 
added.  The  vessel  is  closed  by  a  three-holed  cork,  in  the  middle  hole  of 
which  is  inserted  a  glass  tube  which  carries  an  efficient  stirrer  ;  the  other 
holes  are  used  for  the  inlet  and  outlet  tubes.  After  the  apparatus  has  been 
firmly  fastened  in  a  clamp,  it  is  immersed  in  a  jar  filled  with  water  at  20°. 
A  current,  not  too  rapid,  of  carbon  monoxide  and  hydrogen  chloride 
kis  led  in  through  a  prong-shaped  tube  while  the  stirrer  is  set  in  motion. 
The  gases  are  dried  by  bubbling  each  through  cone,  sulphuric  acid,  their 
rates  of  entry  being  so  regulated  that  the  volume  of  carbon  monoxide  is 
about  twice  that  of  the  hydrogen  chloride  passing  in.  The  escaping  gas  is 
led  directly  to  the  hood  opening  of  a  draught  chamber.  In  the  course  of  an 
hour,  when  about  1 — 2  litres  of  carbon  monoxide  have  been  passed  into 
the  mixture,  the  temperature  rises  to  25° — 30°  ;  the  remainder  of  the  gas 
is  passed  in  during  4 — 5  hours.  Should  the  reaction  mixture  become  so 
viscous  before  the  lapse  of  this  time  that  the  stirrer  revolves  only  with 
difficulty,  the  reaction  may  be  stopped.  The  viscid  product  is  then 
poured  into  a  large  flask  containing  crushed  ice  ;  the  aldehyde  formed, 
and  any  unattacked  toluene  is  distilled  over  with  steam.  The  distillate — 
oil  and  water — is  then  shaken  up  with  a  sodium  bisulphite  solution  (see 
p.  506)  for  a  long  time,  and  the  toluene  which  does  not  dissolve  is 


8G 


SYSTEMATIC  OKGANIC  CHEMISTRY 


separated  in  a  funnel.  If  the  aldehyde-bisulphite  compound  should 
crystallise  out,  water  is  added  till  it  dissolves.  The  filtered  aqueous 
solution  is  then  treated  with  anhydrous  sodium  carbonate  until  it  shows  a 
decided  alkaline  reaction,  the  aldehyde  distilled  off  in  steam,  extracted 
with  ether,  the  extract  dried  over  anhydrous  calcium  chloride,  and  the 
ether  removed  on  a  water  bath. 

CH3.C6H4.H  +  Cl.CO.H  =  CH3.C6H4.CHO.  +  HC1. 

Yield. — 60%  theoretical  (22  gms.).  Colourless  liquid  ;  characteristic 
odour  ;  B.P.  204°.    (B.,  30,  1622  ;  31,  1149  ;  A.,  347,  347.) 

Reaction  XXI.  (a)  Dry  Distillation  of  the  Barium  or  Calcium  Salt  of  a 
Fatty  Acid  with  Barium  or  Calcium  Formate. — This  is  one  of  the  methods 
by  which  aldehydes  may  be  obtained  from  acids.  Like  most  dry  distil- 
lations, the  yields  are  poor,  and  the  method  is  seldom  used. 


CH3- 
H.CO. 


CO.O.Ca.O.i  CO — CH3 

i         =       2CH3.CHO  +  2CaC03. 
O.Ca.O.CO!  H 


Reaction  XXI.  (b)  Dry  Distillation  of  the  Barium  or  Calcium  Salts  of 
Fatty  Acids.  (Z.  Ch.,  19,  1755.)— This  is  an  old  method  of  preparing 
ketones,  and  is  still  used.  Originally  calcium  salts  were  employed,  but 
barium  salts  have  been  found  to  give  better  yields.  Mixed  ketones  can 
be  prepared  by  distilling  an  intimate  mixture  of  the  salts  of  two  acids,  but 
the  symmetrical  ketones  from  the  single  acids  are  also  formed  at  the  same 
time.  The  method  is  perfectly  analogous  to  that  given  above  for  alde- 
hydes. Almost  all  of  the  fatty  acids  give  this  reaction,  but  it  is  better  to 
distil  under  reduced  pressure  when  working  with  the  higher  members  of 
the  series.  If  the  salt  of  a  dibasic  acid  be  used,  since  the  two  carboxyls 
are  already  linked  together,  distillation  produces  a  ring  compound.  This 
is  a  very  important  method  of  ring-formation,  and  series  for  a  very  large 
variety  of  compounds.  The  following  examples  will  give  an  idea  of  the 
scope  of  the  reaction — 

(i.)      CH3.CO.  i  O.Ca.O.CO.  i  CH3 

-I-  ->  2CH3.CO.C6H5  +  2CaC03. 

C6H5.  |  CO.O.Ca.O.  |  CO.C6H5. 

Some  (CH3)2CO  and  (C6H5)2CO  are  also  formed. 

(ii.)      CH2  — CH2— CO  i  0\  CH2 — CH2 — CO 

j   /Ca         |  I      +  CaC03. 

CH2— CH2— !  COO  /  CH2—  CH2 

(hi.)  /CH2 — CO.O  \^  /CH2X 

C8H14  —  CO.O/Ca_>  C8H14—  —CO  +  CaC03. 

(hi.)  represents  the  last  step  in  the  synthesis  of  camphor  by  heating 
calcium  homo-camphorate  in  a  current  of  carbon  dioxide  (Z.  Ch.,  19,  1755). 
Preparation  33 —Acetone  (2-Propanon). 

CH3COCH3.       C3H60.  58. 

100  gms.  (2  mols.)  of  anhydrous  calcium  or  barium  acetate  are  distilled 


CAEBON  TO  CARBON 


87 


from  a  metal  retort  attached  to  a  long  condenser,  some  dry  iron  turnings 
being  previously  mixed  with  the  salt  to  distribute  the  heat.  When  no 
more  liquid  distils,  the  distillate  is  shaken  for  5  hours  with  three  volumes 
of  saturated  sodium  bisulphite  solution  (see  p.  506).  The  crystalline 
compound  is  filtered  off,  dissolved  in  the  minimum  quantity  of  water. 
Anhydrous  sodium  carbonate  is  added  until  the  solution  is  alkaline,  and 
the  acetone  then  distilled  from  a  water  bath.  The  distillate  is  dried  over 
calcium  chloride  and  redistilled,  the  fraction  55° — 59°  being  retained. 


CH3CO 
CH, 


0  Ca  0.  OC 
CO  .  0  Ca  0 


CH3 


Yield. — 20%  theoretical  (7*5  gms.)  from  calcium  acetate  ;  25%  theo- 
retical (10  gms.)  from  barium  acetate.  Colourless  mobile  liquid  ;  B.P. 
56-3°  ;  D.  ^  0-742  ;  soluble  in  water. 

The  distillate  may  also  be  purified  by  adding  an  equal  volume  of  water 
to  dissolve  the  acetone,  dehydrating  for  several  hours  over  quicklime  under 
a  reflux,  distilling,  and  dehydrating  further  over  calcium  chloride. 

Preparation  34. — Benzophenone  (1-Phenyl-l-ethanon). 

C6H5.CO.C6H5.       C13H10O.  182. 

10  gms.  (2  mols.)  of  benzoic  acid  are  heated  to  boiling  with  25  gms. 
(excess)  of  slaked  lime  and  ten  times  the  weight  of  water,  until  the  acid  is 
completely  dissolved  and  the  liquid  reacts  alkaline.  It  is  then  filtered  hot 
from  the  excess  of  slaked  lime.  On  cooling  most  of  the  calcium  benzoate 
separates  out  from  the  filtrate  in  white  needles.  The  remainder  is  ob- 
tained on  evaporating  the  mother  liquor.  The  salt  is  filtered  as  well  as 
possible  at  the  pump,  pressed  by  means  of  the  press,  and  completely  dried 
in  metal  dishes  over  a  free  flame. 

The  mass  is  now  introduced  into  a  metal  retort  (made  of  iron  or  copper), 
which  is  connected  with  a  long  condenser-tube.  The  retort  must  not  be 
filled  more  than  two-thirds  full.  It  is  heated  over  a  powerful  gas  burner, 
so  that  the  dry  distillation  of  the  salt  proceeds  as  quickly  as  possible.  A 
pale  brownish  coloured  mixture  of  benzene,  benzophenone  and  aromatic 
products  first  distils  over.  The  distillation  is  stopped  when  the  distillate 
becomes  brown  and  viscous.  The  distillate  is  dried  with  calcium  chloride, 
and  then  fractionated.  The  fraction  250° — 310°  contains  the  benzo- 
phenone. The  product  sometimes  soon  solidifies,  but  more  frequently 
remains  syrupy  for  days.  Crystallisation  begins,  however,  at  once, 
when  a  small  quantity  of  solid  benzophenone  is  added.  The  crystals  are 
freed  from  the  oily  mother  liquor  by  pressing  between  filter  paper,  or  by 
spreading  on  a  porous  tile,  and  are  recrystallised  from  ligroin. 

2C6H5COOH  ->  (C6H5COO)2Ca  ->  (C6H5)2CO. 

Yield. — 30%  theoretical  (20  gms.)  (see  p.  83). 

Reaction  XXI.  (c)  Action  of  Acetic  Anhydride  on  Carboxylic  Acids,  and 
subsequent  Distillation. — This  method  of  preparing  ketones  is  worthy  of 


88 


SYSTEMATIC  ORGANIC  CHEMISTRY 


note  because  it  was  used  to  obtain  S-ketohexahydrobenzoic  acid  from 
4-carboxyl-heptan-di-acid. 

COOH  OOOH  CO 


CH2  CH2 


CH, 


CH. 


CH, 
CH, 


CH„  CH., 

/     -  CH 


CH 


COOH 


COOH 

6-Ketohexahydrobenzoic  acid  is  important,  because  it  is  the  starting 
point  in  one  of  the  methods  of  synthesising  terpenes  (see  p.  68). 

Reaction  XXI.  (d)  Catalytic  action  of  its  Manganese  Salt  on  the  vapour 
of  a  Fatty  Acid. — When  acetic  acid  vapour  is  passed  over  heated  manga- 
nese acetate,  acetone  is  formed.  The  process  is  continuous  and  the  method 
gives  better  yields  than  the  older  distillation  method.  The  cycle  of  changes 
which  takes  place  in  the  action  may  be  formulated  somewhat  as  follows — 

Mn.(O.OC.CH3)2  =  (CH3)2CO  +  MnC03. 
MnC03  +  2CH3COOH  =  Mn.(O.OC.CH3)2  +  C02  +  H20,  and  so  on. 

The  principle  of  this  method  has  been  utilised  on  the  industrial  scale, 
and  with  success  for  the  preparation  of  acetone.  The  acetic  acid  may  be 
prepared  from  acetylene  via  acetaldehyde  (see  p.  426)  thus  providing 
a  commercial  synthesis  of  acetone  from  coke. 

Preparation  35. — Acetone. 

CH3.CO.CH3.       C3H60.  58. 

About  20  gms.  of  manganous  carbonate  are  made  into  a  thick  paste  with 
water  in  a  basin.  This  is  stirred  with  an  equal  bulk  of  pumice  in  small 
pieces,  and  then  placed  in  an  air  oven  at  110° — 120°  until  quite  dry. 
When  dry  it  is  loosely  packed  into  a  combustion  tube,  sufficient  being 
taken  to  fill  rather  more  than  half  (40  cms.), the  length  of  the  tube  ;  two 
asbestos  plugs  are  used  to  keep  the  layer  in  position. 

The  combustion  tube  is  then  placed  in  a  long  cylindrical  air  bath  (see 
Fig.  43).  The  side  tube  of  a  distilling  flask  containing  acetic  acid  is 
inserted  through  an  ordinary  cork  in  one  end  of  the  combustion  tube. 
The  other  end  of  the  combustion  tube  may  be  bent  and  drawn  out  after 
the  fashion  of  an  adapter,  or  it  may  be  fitted  with  a  cork  and  delivery 
tube  ;  in  either  case  it  is  connected  to  an  apparatus  for  condensing  the 
mixture  of  acetone  and  acetic  acid  which  passes  over  (see  p.  47  for  con- 
denser arrangement).  The  air  bath  is  heated  to  120°— 130°  and  main- 
tained at  this  while  the  combustion  tube  is  filled  with  the  vapour  of  acetic 
acid  by  boiling  the  acetic  acid  in  the  distilling  flask  for  a  few  minutes. 
The  air  bath  is  then  raised  to  400° — 450°,  i.e.,  until  the  bottom  of  the  air 
bath  is  at  a  good  red  heat  (N.B.,  a  thermometer  should  not  be  used  unless 
it  is  nitrogen  rilled).  Shields  of  thick  asbestos  paper  should  be  placed  over 
the  air  bath  to  conserve  heat.  The  distillate  which  collects  in  the  receivers 
(the  second  receiver  should  be  cooled  in  ice),  consists  of  acetic  acid,  acetone 


CARBON  TO  CARBON 


89 


and  water.  If  this  distillate  is  passed  a  second  or  third  time  over  the 
catalyst,  the  yield  of  acetone  is  increased.  In  this  way  excellent  yields 
may  be  obtained.  The  final  distillate  is  distilled  from  an  apparatus  on  a 
water  bath,  using  a  thermometer  and  efficient  condenser,  collecting  what 
distils  up  to  80°  ;  this  is  dried  in  contact  with  solid  potassium  carbonate 
and  fractionally  distilled.    B.P.  of  acetone  56°. 

CH3COOH  +  HOOC.CH3  =  CH3.CO.CH3  +  C02  +  H20. 
(See  p.  87.) 

Reaction  XXII.  (a)  Action  of  Magnesium  Alkyl  or  Aryl  Halide  on  (i.) 
excess  of  Ethyl  Formate,  (ii.)  Ethyl  Orthoformate,  (hi.)  di-substituted 
formamide  and  other  Derivatives  of  Formic  Acid  (Grignard). — This  is  the 
Grignard  method  of  preparing  aldehydes.  The  same  remarks  apply  to 
this  reaction  as  to  the  other  "  Grignards  "  dealt  with.  The  equations 
illustrate  its  course. 

(i.)  H.COOC2H5  +  C6H5MgI  ->  C6H5CHO  +  C2H6O.Mg.I. 

(ii.)  H.C(OC2H5)3  +  C6H5MgI  ->  C6H5CHO  +  C2H5OMgI 

+  H20.  +  2C2H5OH. 

(iii.)  H.CO.N(CH3)2  +  C6H5MgI  ->  HC(C6H5)(OMgI)N(CH3) 

->  C6H5CHO  +  (CH3)2NH  +  Mg(OH)I. 

The  course  of  the  above  reaction  should  be  studied  carefully,  as  it  is 
somewhat  different  from  those  so  far  discussed. 

Reaction  XXII.  (b)  Action  of  Magnesium  Alkyl  or  Aryl  Halide  on 
(i.)  Nitriles,  and  (ii.)  Amides  (Grignard). — This  is  the  analogous  reaction 
to  the  foregoing,  ketones  being  obtained  in  place  of  aldehydes  by  using 
derivatives  of  acids  other  than  formic.  The  esters,  however,  do  not 
figure  among  the  derivatives  which  can  be  employed  (see  p.  70). 

/* 

CN  C  =  NMgl 

I     +  2EMgI  ->  I 

CN  C  =  NMgl 

C  =  NH  C  =  0 


(i.) 


+  2Mg(OH)I  1H_^  +  2NH3- 

C  =  NH  C  =  0 

/C2H5 

C6H5CN  +  C2H5MgI  ->  C  =  NMgl  -> 


C6H5.CO.C2H5  +  NH3  +  Mg(OH)I. 

(ii.)  C6H5CONH2  +  CH3MgI  ->  C6H5C(CH3)(OMgI)NH2 

->  C6H5.CO.CH8  +  Mg(OH)I  +  NH3. 

These  reactions  are  of  theoretical  rather  than  of  practical  interest. 


90 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Reaction  XXII.  (r)  Action  of  Zinc  Alkyl  on  Acyl  Chlorides  in  certain 
proportions. — The  preparation  of  alcohols  by  this  method  has  already 
been  discussed  (Reaction  XV).  By  using  only  1  mol.  of  zinc  alkyl 
to  2  mols.  of  acid  chloride,  the  reaction  can  be  stopped  at  the  inter- 
mediate ketone  stage.  In  the  Grignard  reaction  with  acid  chlorides,  it 
has  not  been  found  possible  to  do  this  owing  to  the  greater  reactivity  of 
the  Grignard  compounds. 

2CH3.CO.Cl  +  Zn(CH3)2  =  2CH3COCH3  +  ZnCl2. 

Reaction  XXIII.  (a)  Condensation  of  Ethyl  Formate  with  certain  Oxy 
Compounds  under  the  influence  of  Sodium  Ethoxide  (Claisen).  (A.,  283, 
306.) — This  condensation  is  undergone  by  all  compounds  containing  the 
group  — CH2 — CO—.  It  follows  the  same  lines  as  the  other  ester-ketone 
condensations  (see  p.  137  et  seq.). 

COR  COR 

!  I 

R.CH2  +  C2H5O.O.C.H  ->  R.CH.CHO  +  C2H5OH 

COR 
I 

->  R.C  :  CH(OH)  +  C2H5OH. 

The  compounds  so  formed  were  at  first  thought  to  be  aldehyde  deriva- 
tives, thus  the  compound  derived  from  acetophenone  was  thought  to  have 
the  formula — C6H5COCH2CHO.  Support  was  lent  to  this  view  by  the  fact 
that  the  compound  gave  an  oxime,  C6H5.CO.CH2.CH  :  NOH.  On  the 
other  hand  in  many  reactions  it  behaved  as  if  it  had  the  formula  C6H5 
COCH  :  CH(OH).  It  gave  a  sodium  salt,  being  obtained  as  such  in  its 
preparation  ;  and  a  chloro  compound,  C6H5COCH  :  CHC1,  when  treated 
with  PC15.  The  view  now  held  is  that  these  "  hydroxymethylene  "  com- 
pounds are  tautomeric  ;  both  oxy  and  enol  forms  being  present.  The 
enol  form  is  of  special  interest  on  account  of  the  great  reactivity  of  the 
hydroxyl  group.  The  double  bond  seems  to  have  the  same  activating 
effect  as  the  oxy  group  in  carboxyl  compounds,  the  hydroxyl  group 
behaving  more  like  an  acid  hydroxyl  than  an  alcoholic.  The  chloride 
derived  from  it  is  nearly  as  reactive  as  an  acid  chloride  ;  and  the 
corresponding  amino  compound  behaves  rather  as  an  amide  than  as  an 
amine. 

The  compounds  separate  from  the  condensation  as  sodium  salts. 
From  the  simple  ketones,  the  compound  formed  is  not  stable  and, 
undergoes  change  on  precipitation  from  its  sodium  salt.  The  formation 
of  a  hydroxymethylene  compound  is  used  as  proof  of  the  presence  of  the 
group  — CH2 — CO —  in  camphor.  The  following  preparation  shows  the 
details  of  the  method. 

Preparation  36.— Camphor  Aldehyde  (Hydroxymethylene  Camphor). 


CO  /CO 
and  C8II  , , 

CH.CHO  XC  =  CH(OH). 


C8H14  and  C8H14  CnH1602.  180. 


CARBON  TO  CARBON 


91 


90  gms.  (excess)  of  camphor  are  dissolved  in  toluene  which  has  been 
freed  from  water  by  standing  over  calcium  chloride,  and  to  this  solution  are 
added  6  gms.  of  sodium  wire.  To  the  well  cooled  mixture  19  gms.  (1  mol.) 
ethyl  formate  are  added,  when  it  is  set  aside  in  an  ice  chest  for  24  hours. 
It  is  then  poured  into  ice  water,  and  after  vigorous  shaking,  the  aqueous 
layer  removed.  After  acidifying  with  acetic  acid,  and  then  extracting 
with  ether,  the  ethereal  extract  is  dried  over  calcium  chloride.  The  ether 
is  removed  by  distillation,  and  the  residue,  after  being  placed  in  a  basin, 
is  allowed  to  evaporate  slowly  at  ordinary  temperature.  The  oil  which 
remains  solidifies  on  standing  to  colourless  crystals. 

/CO  /CO 
C8H14     j      +  C2H5ONa  +  H.COOC2H5  ->  C8H14     |  +  2C2H5OH 

^CH2  ^C  =  CH(ONa) 

/CO  /co 
^  C8H14  ~ >    C8H14  | 

XxC  =  CH(OH)  \  CH.CHO. 

Yield.— Theoretical  (46  gms.).  Soluble  in  ether  ;  M.P.  77°.  (A.,  283, 
306.) 

Reaction  XXIII.  (b)  Condensation  o£  Esters  other  than  Ethyl  Formate, 
with  certain  Ketones  under  the  influence  of  Sodium  Ethylate,  Metallic 
Sodium,  or  Sodamide  (Claisen).  (B.,  22,  1009  ;  23,  R.,  40 ;  38,  695.)— 
This  is  a  similar  reaction  to  that  discussed  above,  and  is  part  of  a  general 
condensation  undergone  by  esters  with  oxy  compounds,  other  phases  of 
which  will  be  found  discussed  on  pp.  137-145. 

The  reaction  may  be  formulated  as  follows — 

EiCOOEt  +  H^CEnCOCEm  =  E^CO.CEjjCOCEm  +  Et.OH. 

where  R  may  be  hydrogen  or  an  alkyl  or  aryl  group.    It  is  only  these 

i 

ketones  which  possess  the  group  HC — CO —  that  undergo  the  reaction. 

The  compound  formed  is  always  a  1  :  3-di-ketone.  The  way  in  which 
the  condensing  agent  used  brings  about  the  condensation  is  described 
under  the  actual  preparations  (see  Preparation  37).  The  compounds 
themselves  are  di-ketones,  but  their  sodium  salts  are  derived  from  the 
corresponding  enol  compounds  (B.,  25,  3074).  Of  the  three  condensing 
agents  used,  sodamide  is  the  most  and  sodium  ethylate  the  least  effective. 
Prepakation  37. — Benzoyl  Acetone  (1-Phenyl-l :  3-di-oxybutan). 

C6H5.CO.CH2.CO.CH3.       C10H10O2.  162. 

Method  I. — 6  gms.  (1  mol.)  of  fresh  dry  sodium  ethylate  (see  p.  505) 
are  added  to  20  gms.  (excess)  of  dry  ethyl  acetate  under  cooling  by  water. 
After  15  minutes,  10  gms.  (1  mol.)  of  acetophenone  are  added  ;  the 
separation  of  the  sodium  salt  of  benzoyl  acetone  immediately  begins.  A 
little  dry  ether  is  added,  and  in  4  hours  the  sodium  compound  is  filtered 


92 


SYSTEMATIC  ORGANIC  CHEMISTRY 


off,  washed  with,  ether,  air-dried,  dissolved  in  cold  water,  and  the  solution 
acidified  with  acetic  acid.    Benzoyl  acetone  separates. 

(1)  CH3COOEt  +  C2H5ONa 

/ONa 

=  CH3C— OC2H5 
/ONa 

(2)  CH3C  —  OC2H5  +  CH3COC6H5 

^OC2H5 

=  CH3C(ONa)  :  CH.CO.C6H5.+  2C2H5OH. 
CH3C(ONa)  :  CH.CO.C6H5  +  CH3.COOH 
=  CH3CO.CH2CO.C6H5  +  CH3COO.Na. 

Yield. — 66%  theoretical  (10  gms.).  Colourless  crystals;  insoluble  in 
water  ;  M.P.  61°  ;  gives  a  deep  violet  coloration  with  ferric  chloride 
and  a  bluish-green  crystalline  precipitate  of  copper  benzoyl  acetone  with 
alcoholic  copper  acetate.  This  shows  the  compound  to  be  tautomeric,  a 
little  of  the  enol  form  being  present  at  ordinary  temperatures.  The 
acidity  of  the  hydroxyl  group  in  the  enol  form  is  not  so  marked  as  it  is  in 
the  case  of  the  hydroxymethylene  compounds  ;  nevertheless,  the  metallic 
salts  of  benzoyl  acetone  and  such  di-ketones  are  remarkably  stable,  and 
on  account  of  their  great  crystallising  power  have  been  used  for  the 
determination  of  the  valency  and  atomic  weight  of  the  rare  elements. 
They  are  also  of  importance  in  the  theory  of  co-ordinating  valencies.  (C, 
1900,  L,  588  ;  B.,  34,  2584.) 

Method  II. — 25  gms.  (excess)  of  ethyl  acetate  and  30  gms.  of  aceto- 
phenone  (1  mol.)  are  dissolved  in  200  c.cs.  of  anhydrous  ether.  To  this  is 
slowly  added  with  gentle  cooling  20  gms.  (excess)  of  powdered  sodamide. 
It  is  then  set  aside  for  24  hours,  when  the  sodium  salt  separates,  and 
is  poured  on  to  a  mixture  of  ice  and  water  sufficient  completely  to 
dissolve  it.  The  aqueous  layer  is  separated,  and  the  ether  removed  from 
it  by  passing  air  through.  Acetic  acid  is  then  added  until  the  solution  is 
acid,  the  precipitated  benzoyl  acetone  being  filtered  off  and  washed  with 
water. 

/ONa 

CH3COOC2H5  +  NaNH2  ->  CH3C  —  OC2H5. 

XNH2 

/ONa 

CH3C  —  OCoH5  +  CH3COC6H5  ->  CH3C(ONa)  :  CH.COC6H5 
\NH2  +  C2H5OH  +  NH3. 

CH3C(ONa) :  CH.COC6H5  +  CH3COOH  ->  CH3C(OH)  :  CH.COC6H5 

+  CH3COONa. 

CH3C(OH)  :  CHCOC6H5  ^  CH3COCH2COC6H5. 

Yield—  75%  theoretical  (30  gms.).  Colourless  crystals;  M.P.  61°; 
insoluble  in  water.    (B.,  36,  695.) 

Thus  the  yield  is  improved  by  using  ether  as  a  solvent,  and  by  replacing 
sodium  ethylate  by  sodamide. 


CARBON  TO  CARBON 


93 


Reaction  XXIV.  Condensation  of  certain  Oxy-Compounds  with  one 
another  under  the  influence  of  Dehydrating  Agents.  (A.,  223,  139.) — 
Aldehydes  and  ketones  readily  condense  with  one  another  under  the 
influence  of  such  reagents  as  zinc  chloride,  hydrochloric  acid,  sulphuric 
acid,  alkali  hydroxides,  sodium  acetate  solution,  etc.,  to  give  a-,  /3-olefinic 
aldehydes  and  ketones : 

The  reaction  may  be  divided  into  the  following : — 

(i.)  Two  aldehydes  condense  to  give  an  olefinic  aldehyde.  Acetaldehyde 
by  treatment  with  zinc  chloride  yields  crotonaldehyde.  (B.,  14,  514  ;  25, 
R.,  372.) 

CH3CHO  +  CH3CHO  ->  CH3CH(OH)CH2CHO  ->  CH3CH  =  CHCHO. 

By  using  condensing  agents  which  are  not  at  the  same  time  dehydrating 
agents,  the  intermediate  aldol  compound  can  be  isolated  (see  p.  95).  A 
mixture  of  acetaldehyde  and  benzaldehyde  yields  cinnamic  aldehyde  by 
the  action  of  hydrogen  chloride,  sodium  hydrate,  or  sodium  ethylate.  (B., 
17,2117;  20,657.) 

C6H5CHO  +  CH3CHO  ->  C6H5CH  =  CHCHO  +  H20. 

Piperonyl  acrolein  is  obtained  from  piper onal  and  acetaldehyde.  This  is 
the  initial  step  in  the  synthesis  of  piperine,  one  of  the  first  alkaloids 
synthesised.    (B.,  27,  2958.) 

0/\CHO  0/\CH  :  CH.CHO. 


H2CO<  +  CHg.CHO  ->  H2C  < 

MX   >  X0 


(ii.)  An  aldehyde  and  a  ketone  or  two  ketones  condense  to  yield  an 
olefinic  ketone. 

Citral  and  acetone  give  pseudo-ionone.  (B.,  27,  R.,  768  ;  see  Reaction 
XVIII.  (iv.)  .) 

(CH3)2C  :  CHCH2CH2C(CH3)  :  CHCHO  +  CH3COCH3 
->  (CH3)2C  :  CHCH2CH2C(CH3)  :  CHCH  :  CHCOCH3. 

Acetone  yields  mesityl  oxide.    (A.,  178,  351.) 

CH3.CO.CH3  +  CH,.CO.CH3  ->  (CH3)2C  :  CHCOCH3. 

Hydrochloric  acid  is  best  suited  for  this  condensation  ;  the  acetone 
being  saturated  with  it  in  the  cold. 

(hi.)  Several  molecules  of  the  same  ketone  may  condense  to  yield  di- 
and  poly-olefimc  ketones.  (B.,  36,  2555  ;  C,  1903,  II.,  566.)  Three 
molecules  of  acetone  form  phorone. 

3CH3COCH3->(CH3)2C  =  CH.CO.CH  =  C(CH3)2. 

Preparation  38. — Benzylidene  Acetone  (l-Phenyl-3-on-l-buten). 

C6H5CH  :  CH.CO.CH3.       C10H10O.  146. 

2  gms.  (1  mol.)  of  benzaldehyde  and  3-5  gms.  (excess)  of  acetone  are 
heated  with  20  c.cs.  of  10%  caustic  soda  solution  on  a  water  bath  for  1  hour. 


94 


SYSTEMATIC  ORGANIC  CHEMISTRY 


The  crystals  which  separate  on  cooling  are  filtered  of!  and  fecrystalHsed 
from  a  little  alcohol. 

C6H5.CHO  +  CH3.CO.CH3      C6H5CH  :  CH.CO.CH3  +  H20. 

Yield. — Theoretical  (3  gms.).  Colourless  crystals  ;  dissolve  with  an 
orange  red  colour  in  sulphuric  acid  ;  M.P.  42°  ;  B.P.  262°.  (A.,  223,  139  ; 
B.,  6,  254.) 

0-  and  jo-nitrobenzylidene  acetones  can  be  prepared  in  the  same  way 
from  0-  and  ^-nitrobenzaldehydes  respectively.  They  melt  at  60°  and  110°. 

Peeparation  39 .— Benzylidene  Acetophenone  (l-3-Diphenyl-3-on-l- 
propen). 

C6H5.CH  :  CH.CO.C6H5.       C15H120.  208. 

2-1  gms.  (1  mol.)  of  benzaldehyde  and  2-4  gms.  (1  mol.)  of  acetophenone 
are  dissolved  in  20  gms.  of  alcohol,  2  gms.  of  10%  caustic  soda  solution  are 
added,  and  the  whole  allowed  to  stand  for  24  hours.  The  precipitate  is 
recrystallised  from  ligroin. 

C6H5CHO  +  CH3COC6H5  =  C6H5CH  :  CH.CO.C6H5  +  H20. 

Yield.— Theoretical  (4  gms.).  Colourless  crystals  ;  M.P.  57°— 58°  ; 
B.P.  346°.    (B.,  20,  657.) 

Reaction  XXV.  Action  of  an  Alkyl  Halide  on  the  Sodio-derivative  of 
certain  Ketones.  (B.,  21,  1297  ;  23,  2072.)— The  fact  that  two  phenyl 
groups  have  something  of  the  same  acidifying  influence  as  one  carbonyl 
group  is  shown  in  the  case  of  desoxybenzoin,  C6H5.CO.CH2C6H5  ;  one 
of  the  two  methylene  hydrogens  in  this  compound  is  replaceable  by 
sodium  and  with  the  sodium  compound,  the  same  kind  of  synthesis  may 
be  effected  as  with  sodio  aceto-acetic  ester.  The  methylene  group 
behaves  as  if  it  were  between  two  carbonyl  groups,  except  that  the  second 
methylene  hydrogen  is  not  replaceable. 

Na 

C6H5.CO.CH2C6H5  >  C6H5.C  :  CHC6H5 

ONa 

C2H5I 

 >  C6H5.CO.CH(C2H5)C6H5. 

Desoxytoluoin  CH3  .  C6H4  .  CH2  .  CO  .  C6H4  .  CH3  and  desoxyanisoin 
CH3O  .  C6H4  .  CH2CO  .  C6H4OCH3  behave  similarly,  as  do  all  the  phenyl- 
benzyl  ketones. 


CHAPTER  VI 


carbon  to  carbon 
Hydroxy-Oxy  Compounds 

The  reactions  below  are  those  in  which  carbon  atoms  are  linked  together 
to  give  compounds  containing  both  a  hydroxyl  and  an  oxy  group.  In  the 
aliphatic  series  there  are  three  main  divisions  of  such  compounds  : — 

(a)  The  oxy  group  is  linked  to  a  terminal  carbon,  and  the  hydroxyl 
group  to  another  carbon — aldols. 

(6)  The  oxy  group  is  linked  to  a  non-terminal  carbon,  and  the  hydroxy] 
group  to  another — ketols. 

(c)  The  oxy  group  is  linked  to  the  same  carbon,  necessarily  terminal — ■ 
as  the  hydroxyl  group — acids. 

The  above  only  applies  to  the  simplest  hydroxy-oxy  compounds  ;  acid- 
ketols,  ketaldols,  and  acid  ketaldols  also  exist. 

The  terms  aldol  and  ketol  are  not  usually  applied  in  the  aromatic  series, 
but  there  is  no  reason  why  salicylaldehyde,  for  instance,  should  not  be 
termed  an  aldol — or  an  aldphenol,  if  it  is  desired  to  restrict  "  ol  "  to  purely 
alcoholic  hydroxy  Is. 

Reaction  XXVI.  (a)  Condensing  Action  of  Potassium  Cyanide,  Potas- 
sium Carbonate,  or  other  substances  on  Aliphatic  (Claisen),  and  Aromatic 
Aldehydes  (Liebig).  (J.  S.  C,  117,  324.) — With  aliphatic  and  aromatic 
aldehydes  this  condensation  follows  very  different  lines.  In  the  former 
the  condensation  takes  place  between  the  aldehydic  carbon  of  one  molecule 
and  the  a-carbon  of  another  molecule.  The  same  or  different  aldehydes 
may  be  used. 

2R1RCH.CHO  =  RR1CH.CH(OH).C(RR1).CHO. 
R.CH2.CHO  +  R^HO  =  R1CH(OH).CH(R).CHO. 

It  will  be  seen  that  only  an  aldehyde  with  at  least  one  a-hydrogen  can 
condense  with  itself  or  with  another  aldehyde.  This  latter,  however,  need 
have  no  particular  structure.  Condensing  agents  stronger  than  those 
mentioned  above  ehminate  water  if  possible,  after  condensation.  Two 
a-hydrogen  atoms  in  an  aldehyde  are  necessary  for  this  reaction  (see 
Eeaction  XXIV.). 

It  is  worth  noting  that  if  the  aldol  condensation  takes  place  in  the 
presence  of  magnesium  amalgam,  the  aldehydic  group  is  simultaneously 
reduced  and  a  1  :  3-dihydric  alcohol  is  formed. 

When  aromatic  aldehydes  are  heated  with  potassium  cyanide  in  aqueous 
alcoholic  solution,  the  aldehyde  groups  condense  and  a  ketol  is 
formed.  The  reaction  was  discovered  by  Liebig  for  benzaldehyde  (A.,  3, 
276),  but  was  later  applied  to  other  aromatic  aldehydes  (B.,  25,  293  ; 

95 


96 


SYSTEMATIC  ORGANIC  CHEMISTRY 


26,  60),  and  since  then  some  heterocyclic  aldehydes  have  been  found  to 
undergo  the  reaction.    (B.,  28,  R.,  992.) 

Theoretically  the  reaction  is  supposed  to  take  place  according  to  the 
following  equations — ■ 

/OH 

C6H5.CHO  +  KCN  +  H20  ->  C6H5C  — H  +  KOH. 

Cyanhy  drin. 
/OH  /OH 


CfiHcC 


OH 

—  H 

•CN 


C6H5CHO 


C6H5C 


C  — —  C6H5 


C6H5.CO.CH(OH)C6H5  +  HCN. 
Benzoin. 


Aldol  condensate 


The  action  of  the  potassium  cyanide  is  catalytic,  a  small  quantity  being 
capable  of  condensing  a  large  quantity  of  aldehyde. 
Preparation  40. — Aldol. 

CH3.CHOH.CH2.CHO.       C4H802.  88. 

200  c.cs.  of  ice-cold  water  are  placed  in  the  apparatus  (Fig.  47),  which  is 
immersed  in  a  cooling  bath.    100  gms.  of  freshly  distilled  acetaldehyde, 

in  portions  at  a  time,  are  introduced 
while  the  cork  is  momentarily  withdrawn, 
the  bottle  being  agitated  slightly  during 
the  addition,  and  great  care  being  taken 
that  the  temperature  of  the  contents  does 
not  rise  above  0°.  A  suitable  cooling  bath 
for  this  stage  consists  of  ice,  water  and  a 
little  hydrochloric  acid.  When  all  the 
aldehyde  is  added,  the  cooling  bath  is 
replaced  by  one  of  ice  and  hydrochloric 
acid,  and  when  the  temperature  of  the 
contents  of  the  bottle  has  fallen  to  —  12°, 
100  c.cs.  of  a  2-5%  solution  of  potassium 
cyanide  are  slowly  dropped  in  while  the 
bottle  is  rotated  ;  the  temperature  must  be 
kept  below  —  8°.  After  the  cyanide  is 
added,  the  mixture  is  kept  for  2  hours 
below  —8°,  the  freezing  mixture  being 
renewed  if  necessary,  and  then  for  30  hours 
in  an  ice  chest  at  0°.  The  resulting 
c  syrupy  solution  of  pale  yellow  colour  is 

saturated  in  the  cold  with  common  salt,  and  then  quickly  extracted  four 
times  with  a  moderately  large  volume  of  ether.  The  ethereal  extracts  are 
dried  over  anhydrous  sodium  sulphate,  the  ether  distilled  off,  and  the 
residue  distilled  under  reduced  pressure.  Aldol  passes  over  at  80° — 90° 
and  20  mms.  pressure.    A  suction  flask  containing  cone,  sulphuric  acid 


n 

) 

0 

e 

i 

1 

'  i) 

?u 

m 

w 

Fig.  47. 


CAKBON  TO  CARBON 


97 


should  be  placed  between  the  receiver  and  the  pump  to  absorb  aldehyde 
vapours,  which  would  otherwise  prevent  a  high  vacuum  being  obtained. 
CHg.CHO  +  CH3CHO  -VCH3.CHOH.CH2.CHO. 

Yield. — 50%  theoretical  (50  gms.).  Colourless,  odourless  liquid ; 
D.  J  1-12  ;  B.P.  20  75°.  On  distilling  at  atmospheric  pressure  forms 
acetaldehyde  and  much  crotonaldehyde.  (A.,  306,  323  ;  C,  1907  L, 
1400;  J.  C.  S,  117,  324.) 

Preparation  41. — Benzoin  (l-2-Diphenyl-X-on-2-ol-ethan). 

C6H5.CO.CH(OH).C6H5.  C14H1202.  212. 
21  gms.  (2  mols.)  of  pure  benzaldehyde  and  2  gms.  of  95%  potassium 
cyanide  dissolved  in  80  c.cs.  of  50%  alcohol  are  refluxed  for  an  hour  on  a 
water  bath.  The  crystals  of  benzoin  which  separate  on  cooling  are  filtered 
off  ;  2  gms.  of  potassium  cyanide  are  added  to  the  filtrate  and  a  second 
yield  of  benzoin  obtained  as  before.  The  whole  is  recrystallised  from  hot 
alcohol. 

2C6H5CHO  ->  C6H5CO.CH(OH).C6H5. 

Yield. — 90%  theoretical  (38  gms.).  Colourless  prisms ;  slightly 
soluble  in  water  ;  soluble  in  alcohol  and  ether  ;  M.P.  137°  ;  is  easily 
oxidised  to  benzil  (q.v.).    (A.,  3,  276  ;  34,  187  ;  198,  151.) 

Reaction  XXVI.  (b)  Condensing  Action  of  Potassium  Cyanide  on  a 
mixture  of  an  Aliphatic  Aldehyde  and  a  Ketone.  (A.,  306,  324.) — This  is 
a  reaction  similar  to  the  previous,  a  ketone  and  an  aldehyde  being 
condensed  to  give  a  1  :  3-ketol. 

K-CO-CH^  +  KnCHO  ->  R.CO.CHR1.CH(OH)K11. 

The  ketone  undergoing  condensation  must  have  at  least  one  oc-H.  If 
it  has  two,  then,  on  heating,  these  ketols  eliminate  water  to  give  olefmic 
ketones.  It  is  to  be  noted  that  no  condensation  takes  place  at  the  oxy- 
carbon  of  the  ketone.  An  excess  of  the  ketone  must  always  be  used  to 
prevent  the  condensation  of  two  molecules  of  the  aldehyde  to  an  aldol 
compound.  If  the  reaction  is  carried  out  at  a  high  temperature,  and 
with  more  powerful  condensing  agents,  the  unsaturated  ketone  is  directly 
obtained  (see  Reaction  XXIV.).  (B.,  25,  3165  ;  C,  1297,  I.,  1018  ;  1905, 
II.,  752). 

Preparation  42. — Hydracetyl  Acetone  (Pentanol-(2)-on-(4) ). 

CH3CH(OH)CH2COCH3.  C5H10O2.  102. 
116  gms.  (2  mols.  ;  excess)  of  pure  acetone  are  cooled  to  —12°  (see 
p.  96)  and  treated  with  a  30%  solution  of  5  gms.  of  potassium  cyanide. 
The  mixture  is  then  slowly  stirred  by  mechanical  means,  and  44  gms.  (1 
mol.)  of  freshly  prepared  acetaldehyde  dropped  in,  the  temperature  being 
always  below  —5°.  The  whole  is  allowed  to  stand  for  half  an  hour  in  the 
freezing  mixture  and  8  hours  in  an  ice-chest.  1J  vols,  of  alcohol-free 
ether  are  added,  and  the  lower  layer  of  potassium  cyanide  solution  removed. 
Any  remaining  cyanide  solution  is  extracted  by  washing  twice  with  60  c.cs. 
of  saturated  brine,  and  a  third  time  with  30  c.cs.  to  ensure  nothing  further 
being  removed.  The  washing  solution  is  extracted  several  times  with 
ether  and  the  total  ethereal  solution  dried  for  2  hours  over  anhydrous 

S.O.O.  H 


98 


SYSTEMATIC  ORGANIC  CHEMISTRY 


sodium  sulphate  (calcium  chloride  absorbs  hydracetyl  acetone).  The 
ether  is  removed  under  reduced  pressure  and  the  residue  fractionated  three 
times  under  a  pressure  of  20  mms.,  first  from  60° — 110°,  second  70° — 90°, 
and  third  77°— 79°. 

CH3CHO  +  CH3COCH3->CH3CH(OH)CH2COCH3. 

Yield. — 25%  theoretical  (25  gms.).  Transparent,  viscous  liquid,  mis- 
cible  in  all  proportions  with  water  or  alcohol ;  can  be  salted  out  of  aqueous 
solution  by  potassium  carbonate;  B.P.  76J  176° — 177°  (slight  decom- 
position) ;  B.P.  20  77°— 78°  ;  D.  \8  0-9780.  (A.,  306,  324  ;  B.,  34,  2092  ; 
37,  504.) 

Note  the  use  of  2  mols.  of  acetone  to  prevent  aldol  formation. 

Reaction  XXVII.  Condensation  of  Chloroform  with  Phenols  and 
simultaneous  Hydrolysis  of  the  Product  (Reimer-Tiemann).  (B.,  15,  2585.) 
—This  is  a  well-known  method  for  the  preparation  of  phenolic-aldehydes. 
The  phenol  is  treated  with  chloroform  and  an  alkaline  hydroxide,  when 
the  former  enters  the  ortho-  and  to  a  less  extent  the  ^ara-position  to  the 
hydroxyl  group  ;  hydrolysis  to  an  aldehyde  then  takes  place. 

C6H4  ^ONa 
+  C1.CHC12  +  NaOH  ->  C6H4 


\CHC1. 


l2 

i 

-ONa 


C6H4 

^CH(OH)2 
I 

/OH 

C6H4 

«  \}HO. 

Di-aldehydes  can  be  obtained  from  some  polyhydric  phenols.  Phenolic- 
ethers  also  react  as  do  hydroxy-aldehydes  and  hydroxy-acids. 

Though  it  has  such  a  wide  application,  the  reaction  suffers  from  many 
defects.  The  yields  are  poor,  being  of  the  order  of  20%  theoretical. 
This  is  due  to  the  following  causes  : — 

(a)  A  portion  of  the  phenol  does  not  react  at  all. 

(b)  Some  forms  an  ester  of  ortho-formic  acid — 

3C6H5ONa  +  CHCI3  =  3NaCl  +  CH(OC6H5)3. 

An  excess  of  chloroform  helps  to  prevent  this. 

(c)  A  portion  of  the  aldehyde  first  formed  is  lost  by  condensation  with 
some  unattacked  phenol  to  form  a  derivative  of  triphenyl  methane — 

yCHO  +  2HC6H4OH 
C6H4  =  H20  +  CH(C6H4OH)3. 

A.  non-excess  of  phenol  tends  to  prevent  this. 


CARBON  TO  CARBON 


99 


(d)  The  alkali  tends  to  resinify  the  aldehyde  formed.  Temperature 
control  lessens  this. 

The  Reimer  reaction  is  useless  with  compounds  like  phloroglucinol, 
pyrogallol,  naphthols,  poly-acid  phenols  of  naphthalene,  etc. 

Accordingly,  where  possible  (for  the  j9-hydroxybenzaldehydes),  the 
aluminium  chloride  method  (Reaction  XXVIII.)  should  be  used.  The 
yields  are  better,  the  reactions  go  more  smoothly,  little  resin  being 
formed,  while  pyrogallols  and  naphthols,  etc.,  also  react.  Unfortunately, 
though  the  non-formation  of  other  than  £>-hydroxyaldehydes  is  often  an 
advantage,  it  limits  the  scope  of  the  reaction  and  necessitates  the  use  of  the 
Reimer  method  in  many  cases.  It  should  be  noted  that  the  nitro-phenols 
do  not  condense  with  chloroform  (B.,  9,  423,  824  ;  10,  1562  ;  15,  2685). 

Preparation  43. — Salicylaldehyde  (1 :  2  Hydroxy-benzaldehyde)  and 
1 : 4-Hydroxy-benzaldehyde. 

OH.C6H4.CHO.[l  :  2  and  1  :  4].        C7H602.  122. 

50  gms.  (1  mol.)  of  phenol  and  160  gms.  (excess)  of  caustic  soda  in  160  c.cs. 
of  water  are  heated  to  50° — 60°  in  a  1 -litre  flask  on  a  water  bath  under  a 
reflux.  A  thermometer  dipping  into  the  liquid  is  fitted  to  the  flask. 
75  gms.  (excess)  of  chloroform  are  added,  10  c.cs.  at  a  time,  through  the 
top  of  the  condenser,  the  flask  being  well  shaken  after  each  addition.  By 
alternate  heating  and  cooling  the  temperature  is  kept  at  65°  throughout. 
The  whole  is  then  refluxed  for  half  an  hour,  the  excess  of  chloroform 
removed  on  a  water  bath,  and  the  residue  carefully  acidified  with  dilute 
sulphuric  acid  and  distilled  in  steam  till  no  more  oily  drops  pass  over. 
The  distillate  is  extracted  with  ether,  and  the  extract  shaken  with  twice 
its  volume  of  a  freshly  prepared,  nearly  saturated  solution  of  sodium 
hydrogen  sulphite  for  a  long  time  till  no  more  crystals  separate.  (For 
preparation  of  bisulphite,  see  p.  506.)  The  precipitated  bisulphite  com- 
pound is  filtered  off,  washed  free  from  traces  of  phenol  with  alcohol 
and  decomposed  by  heating  on  a  water  bath  with  dilute  sulphuric  acid. 
The  aldehyde  which  separates  is  extracted  with  ether,  the  extract  washed 
with  water  and  dehydrated  over  anhydrous  sodium  sulphate.  The  ether 
is  removed  on  a  water  bath  and  the  aldehyde  distilled.  Some  ^-hydroxy- 
benzaldehyde  remains  in  the  flask  after  the  steam  distillation.  Tarry 
matter  is  removed  by  filtering  hot  through  a  moistened  filter  paper.  The 
cold  filtrate  is  extracted  with  ether,  the  extract  dried  over  calcium  chloride, 
the  ether  removed  on  a  water  bath,  and  the  residue  recrystallised  from  a 
small  quantity  of  hot  water  containing  sulphur  dioxide. 

C6H5.O.Na  +  3NaOH  +  CHC13  = 
C6H4(ONa)CHO  +  3NaCl  +  2H20. 

Yield. — Salicylaldehyde,  20%  theoretical  (13  gms.)  ;  1  :  ^-Hydroxy- 
benzaldehyde,  4%  theoretical  (3  gms.)  ;  total,  24%  theoretical  (16  gms.). 

Salicylaldehyde. — Colourless  fragrant  oil,  soluble  in  water ;  miscible  in 
all  proportions  with  alcohol  and  ether ;  B.P.  196-5°  ;  solidifies  to  large 
crystals  at  0°  ;  D.^  M72. 

ip-Hydroxybenzaldehyde — Colourless  needles ;  soluble  in  hot  water, 
alcohol  and  ether  ;  M.P.  116°  ;  sublimes.    (B.,  9,  824  ;  15,  2585.) 

H  2 


100  SYSTEMATIC  OKGANIC  CHEMISTRY 


Reaction  XXVIII.  Formation  of  an  Aldime  by  the  action  of  the  com- 
pound of  Hydrogen  Chloride  and  Hydrogen  Cyanide,  HCN.HC1,  on  a  Phenol 
or  a  Phenol  Ether  hi  the  presence  of  Anhydrous  Aluminium  Chloride,  and 
the  Hydrolysis  of  the  Aldime  so  formed  (Gattermann).  (B.,  31,  1765  ; 
32,  271 ;  A.,  357,  363.)— As  stated  in  Reaction  XX.  (d),  the  Gattermann- 
Koch  reaction  does  not  apply  to  phenols  or  phenol  ethers.  If  it  is  desired 
to  obtain  aldehydes  from  them,  hydrogen  cyanide  is  used  in  place  of 
carbon  monoxide,  and  the  mixture  of  anhydrous  hydrogen  cyanide  and 
hydrogen  chloride  is  allowed  to  act  in  presence  of  aluminium  chloride 
alone,  cuprous  chloride  being  unnecessary.  The  crystalline  compound, 
HCLHCN,  which  hydrogen  chloride  forms  with  hydrogen  cyanide,  can 
also  be  used  directly. 

zn 

H.CN  +  HCI    ->  C  =  NH 

Na. 

/0H  AJC13  /0H 

C6H/i  +  ~    >  C6H4 

\E  C1CH  :  NH  \m  :  NH.HC1. 

The  aldime  hydrochloride  so  formed  is  very  easily  hydrolysed  by  acids 
to  the  aldehyde. 

/OK  /OR 
C6H4  +  H20  ->  C6H4  +  NH3. 

\}H  :  NH  N^HO 

Combination  always  takes  place  in  the  ^ara-position  to  the  hydroxyl  or 
alkoxyl  group.  Owing  to  the  difficulty  of  working  with  anhydrous  hydro- 
gen cyanide,  the  method  is  seldom  used  in  the  laboratory. 

Reaction  XXIX.  (a)  Condensation  of  a  Phenol  with  Phthalic  Anhydride 
to  form  a  Phthalein.  (A.,  183,  1 ;  202,  68.)-^-The  phthalei'ns  result  from 
the  condensation  of  phthalic  anhydride  (1  mol.)  with  phenols  (2  mols.) 
on  heating  with  dehydrating  agents — sulphuric  acid,  fused  zinc  chloride 
(to  120°)  or  anhydrous  oxalic  acid  (to  115°).  These  compounds  are 
particularly  important;  some  are  dyes  of  great  technical  value.  The 
simplest  representative  of  the  class  is  phenolphthalem. 

CO 

/\ 

2C6H5OH  +  C6K4/  pO 


CO 

/C6H4(OH)  [1  :  4] 
C  — C6H4(OH)  [1  :  4] 


=  C6H4  /O 

\co 


CAKBON  TO  CARBON 


101 


Thus  the  phthaleins  are  triphenyl  methane  derivatives,  being  all  derived 
from  phthalophenone  (diphenyl  phthalide). 

>(C6H5)2 


C6H4 


o 


(See  p.  81.) 

The  free  phthaleins  are  usually  colourless  crystalline  compounds  dis- 
solving with  intense  colorations  in  alkalis,  but  being  reprecipitated  by 
acids,  even  by  C02.  In  very  concentrated  alkali  they  give  colourless 
solutions.  A  quinone  structure  is  assumed  for  the  coloured  salts,  e.g.,  for 
phenolphthalein  in  alkali  solution. 


CfiH, 


,[1]C 


-C6H4OH 

Xc6H4  =  0 
COOH 


The  phthaleins  derived  from  di-  or  polyhydric  phenols  are  all  anhydrides 
formed  by  the  elimination  of  water  from  two  phenolic  hydroxyls,  attached 
to  two  different  benzene  rings.  These  "  anhydride  phthaleins "  are 
known  as  pyronines,  since  they  contain,  like  the  pyrones,  a  six-membered 
oxygen-containing  ring. 

Even  in  the  preparation  of  phenolphthalein  a  little  of  the  simplest 
pyronine  is  obtained  from  an  or^o-phthalein  first  formed. 


From  resorcinol  the  pyronine  fluorescein  is  the  main  product  (see  p.  378). 
Preparation  44. — Phenolphthalein. 

>(C6H4OH[4])2 


\C6H4C00[2J 


318. 


16  gms.  cone,  sulphuric  acid  is  added  to  a  mixture  of  40  gms.  (excess)  of 
phenol  and  20  gms.  (1  mol.)  of  phthalic  anhydride.  The  mixture  is  heated 
for  9  hours  at  115° — 120°  in  an  oil  bath,  and  the  redoil  formed  poured  into 

0Mk  SoWdl  1 


a 


102  SYSTEMATIC  OKGANIC  CHEMISTKY  ^/ 

jJ   -  . 

a  litre  of  water.  The  phenol  is  removed  by  continued  boiling,  water  being 
added  to  replace  that  lost  by  evaporation.  After  cooling,  the  liquid  is 
filtered  and  the  residue  washed  with  water.  It  is  then  dissolved  in  dilute 
caustic  soda  solution,  and  again  filtered.  The  nitrate  is  acidified  with 
acetic  acid  and  a  few  drops  of  hydrochloric  acid,  and  after  standing  for 
some  time,  the  precipitate  is  filtered  off  and  dried.  It  is  then  remixed  on 
a  water  bath  with  an  excess  of  absolute  alcohol,  a  little  animal  charcoal 
being  added  if  necessary.  After  filtration,  the  residue  is  washed  with 
boiling  absolute  alcohol,  and  the  combined  filtrate  and  washings  evaporated 
to  two  thirds  its  bulk.  It  is  diluted  with  8  vols,  of  water  and  filtered 
through  a  wet  filter  to  remove  resinous  matter.  The  filtrate  is  then  con- 
centrated on  the  water  bath  until  the  phenolphthalein  crystallises. 

2C6H5OH  +  C6H4(CO)20->C(C6H4COO)(C6H4OH)2  +  H20. 

Yield. — 25%  theoretical  (10  gms.).  White  crystalline  powder  ;  M.P. 
250°- — 253°  ;  slightly  soluble  in  cold  alcohol ;  soluble  in  alkalis  to  crimson 
solution.    (B.,  9,  1230  ;  A.,  183,  1  ;  202,  68.) 

Reaction  XXIX.  (b)  Condensation  of  a  Phenol  with  Phthalic  Anhydride 
to  a  derivative  of  Anthraquinone.  (A.,  212,  10.) — When  equimolecular 
quantities  of  phthalic  anhydride  and  a  phenol  react  at  180°  in  the  presence 
of  cone,  sulphuric  acid,  the  product  is  not  a  phthalein,  but  the  action  takes 
a  different  course,  and  a  derivative  of  anthraquinone  is  obtained. 

CO  CO 


C6H4/      \0  +  H2C6H3OH  =  C6H4/       \C6H3OH  ([1]  and  [2]) 
\      /  \  / 


CO  CO 

a  -  and  /3-hydroxyanthraquinone. 

Alizarin  (1  : 2-dihydroxyanthraquinone)  and  an  isomer  hystazarin 
(2  :  3-dihydroxyanthraquinone)  are  also  formed  in  this  way  from  catechol 
and  phthalic  anhydride. 

Preparation  45. — Quinizarin  (1 :  4-Dihydroxyanthraquinone). 

/co\ 

CeH4  C6H2(OH)2[l  :  4].       C14H804.  240. 

W 

40  gms.  (excess)  phthalic  anhydride  and  10  gms.  (1  mol.)  of  pure  quinol 
are  heated  for  3  hours  in  a  flask  in  an  oil  bath  at  170° — 180°  with  200  gms. 
pure  cone,  sulphuric  acid  and  20  c.cs.  of  water.  It  is  then  heated  for  1  hour 
at  190° — 200°.  The  hot  solution  is  gently  poured  into  about  a  litre 
of  cold  water  in  a  large  basin.  The  whole  is  then  heated  to  boiling  and 
filtered  hot  with  suction.  The  residue  is  again  extracted  with  boiling 
water  and  filtered  hot.  It  is  then  boiled  up  with  400  c.cs.  glacial  acetic 
acid  and  filtered  hot,  to  remove  carbonaceous  matter.  The  filtrate  is 
diluted  with  its  own  volume  of  hot  water  and  filtered,  the  residue  being 


CAEBON  TO  CARBON 


103 


again  extracted  with  boiling  glacial  acetic  acid  and  again  precipitated  with 
hot  water.  The  crude  quinizarin  which  separates  on  cooling  is  filtered, 
well  washed  with  water  and  dried  on  a  water  bath.  It  is  then  quickly 
distilled  from  a  hard  glass  retort  with  a  large  name,  a  porcelain  mortar 
being  used  as  receiver.  The  distillate  is  then  powdered  and  recrystalhsed 
from  glacial  acetic  acid  and  washed  with  more  dilute  acetic  acid  and  finally 
with  water. 


C6H4 


'0  +  H2C6H2(OH); 


,co> 


C6H2(OH)2  +  HaO. 


Yield. — 20%  theoretical  (4  gms.).  Dark  red  needles  from  toluene, 
orange  yellow  leaves  from  glacial  acetic  acid ;  M.P.  195°  ;  insoluble  in 
water.    (B,  8,  152  ;  A,  212,  10.) 

Note. — The  quinizarin  which  solidifies  in  the  neck  of  the  retort  may  be 
recovered  by  distilling  some  glacial  acetic  acid  from  the  retort,  a  dis- 
tilling flask  being  used  as  receiver.  Acetic  acid  vapour  is  inflammable, 
so  that  a  rubber  tube  dipping  over  the  side  of  the  bench  should  be  con- 
nected to  the  side  tube  of  the  flask. 

Reaction  XXIX.  (c)  Condensation  of  Meta-hydroxy-  and  di-meta- 
dihydroxy-benzoic  Acids  with  themselves  and  with  Benzoic  Acid  under  the 
action  of  hot  Sulphuric  Acid.  (B.,  18,  2147.) — The  products  of  this  action 
are  like  the  above  hydroxyanthraquinones. 


HCK  VX)OH 


HO 


HOOCv  iOH 


CO 


CO 
CO 


HOOc/NoB 


COOH 


OH 


K)H 


OH 


OH 


OH 


CO  OH 


These  reactions  are  of  interest  as  confirming  the  structure  of  anthra- 
quinone  and  its  hydroxy  derivatives. 

Reaction  XXX.  Condensation  of  a  Nitrile  with  a  Phenol  or  a  Phenol 
Ether  and  Hydrolysis  of  the  resulting  Ketimine  Hydrochloride  to  a  Ketone. 

(J.  C.  S.,  118,  309.) — This  is  a  new  method  of  synthesising  phenolic 
ketones,  and  is  an  extension  of  the  Gattermann  method  for  phenolic 
aldehydes  (Reaction  XXVIII.).   (B.,  43,  1122.) 

In  1915  Hoesch  showed  that  the  condensation  of  a  nitrile  with  a  phenolic 
compound  led  to  the  formation  of  a  ketimine  hydrochloride  which  could  be 
easily  hydrolysed  to  give  a  ketone. 

HC1 

HO.RH  +  EXCN   >  HO.RRj  C  :  NH.HC1 

 >  HO.RRiCO. 

The  phenol  and  the  nitrile  are  dissolved  in  dry  ether,  and  anhydrous 


104  SYSTEMATIC  ORGANIC  CHEMISTRY 


hydrogen  chloride  led  in.  On  standing,  the  hydrochloride  of  the  ketimine 
separates.  Addition  of  fused  zinc  chloride  is  sometimes  advantageous. 
The  ketone  is  obtained  on  heating  or  boiling  the  hydrochloride  with  water. 
The  ketimines  themselves  have  also  been  isolated  in  some  cases.  They 
are  unstable,  and  are  hydrolysed  on  dissolving  in  water. 

C6H5OH  +  C6H5.CH2.CN  -> 

[4]0HC6H5C(NH.HC1)C6H5  -> 
[4]OH.C6H5.CO.C6H5. 

Condensation  takes  place  in  the  ^-position  to  the  hydroxyl  group.  Di- 
and  poly-hydric  phenols  and  phenolic  ethers  can  also  be  employed,  as  can 
hydroxy  and  methoxy  nitriles  (J.  C.  S.,  118,  309). 


CH30r/\0CH3  CH30/\0CH 
+  OHCH2CN  ->  ;  I 


\yCOCH2OH. 


oh/\oh 

+  ch3o.ch2cn  ->  oh/xoh 


OH  WCO.CH2OCH3. 

OH 

It  is  interesting  to  note  that  if  a  hydroxy  nitrile  be  condensed  with  a  di- 
or  poly-hydric  phenol,  cumaron  derivatives  are  obtained  by  elimination 
of  water.    The  methoxy  group  prevents  this. 

OH/\OH  ->  H0/\0H 

+  OHCH2CN 


0 

HO/\/\CH 


\yCOCH2OH 


Ico 


Preparation  46. — w-Methoxyresacetophenone  (l-Methoxy-2-oxy-2- 
(2 : 4-dihydroxy-phenyl-(l)  )-ethan). 

C9H10O4.  182. 


HO,-"  ^OH 

!cO.CH2.OGH3. 


6-5  gms.  (1  mol.)  of  pure  resorcinol  are  dissolved  in  50  c.cs.  of  anhydrous 
ether  and  5  gms.  (1  mol.)  of  methoxyacetonitrile  are  added.  A  current  of 
dry  hydrogen  chloride  is  passed  through  the  solution  for  2  hours,  and 
the  latter  is  allowed  to  stand  in  an  ice-chest  for  5  days.  The  ether  is 
then  poured  off  from  the  yellow  crystalline  ketimine  hydrochloride, 
which  is  washed  twice  with  the  same  solvent  and  recrystallised  from 
methyl  alcohol.  It  forms  a  white  crystalhne  mass  (M.P.  205° — 207°). 
It  is  dissolved  in  water  and  heated  at  80°  (not  more,  or  tarry  matter 


CARBON  TO  CARBON 


105 


i 

separates)  for  30  minutes.  The  solution  becomes  of  a  deep  red  colour. 
On  cooling,  the  ketone  separates  ;  it  is  recrystallised  from  hot  water. 

C6H4(OH)2[l  :  3]  +  CH3OCH2CN  ->  C6H3(OH)2(CO.CH2.OCH3)[l  :  3  :  4]. 

Yield- -70%  theoretical  (8  gms.).  Plates  with  nacreous  lustre ; 
soluble  in  alcohol,  ether,  benzene  ;  insoluble  in  petroleum  ether  ;  reduces 
Fehling's  solution,  forming  a  copper  mirror ;  M.P.  136°.  (J.  C.  S,, 
118,  309.) 

Resacetophenone  can  be  prepared  from  resorcinol  and  acetonitrile  in 
the  very  same  way  in  90%  yield. 

1  gm.  of  fused  zinc  chloride  can  be  added  in  the  above  reaction  either 
initially  or  after  the  passage  of  the  hydrogen  chloride.  It  improves  the 
yield  and  shortens  the  time  of  standing,  but  unless  care  is  taken,  it  tends 
to  cause  decomposition  of  the  product  during  its  isolation. 

Reaction  XXXI.  Action  of  Heat  on  Sodium  Formate.  (B.,  15,  4507.)— 
When  sodium  formate  is  rapidly  heated  above  440°,  an  unusual  reaction 
takes  place.    It  loses  hydrogen  and  forms  sodium  oxalate. 

HCOONa  COONa 

+  =1  +H2. 

HCOONa  COONa 

In  the  presence  of  sodium  hydroxide,  carbonates  or  oxalates,  the  reaction 
takes  place  at  360°  and  to  a  greater  extent.  (C,  1903,  II.,  777  ;  1905,  II., 
367.)  Oxidation  of  formic  acid  with  nitric  acid  similarly  yields  oxalic 
acid.    (B,  17,  9.) 

Reaction  XXXII.   Action  of  Alkalis  on  certain  a-di-ketones.   (A.  25, 

25  ;  31,  324  ;  B.,  14,  326  ;  19,  1868  ;  41,  1644.)— When  benzil  is  fused 
with  potassium  hydroxide,  or  digested  with  alcoholic  potash,  or  heated  for 
a  long  time  with  aqueous  potash,  a  molecular  re-arrangement  not  unlike 
the  pinacoline  transformation  (q.v.)  takes  place,  and  benzilic  acid  is  formed. 

H20 

C6H5CO.CO.C6H5  ->  C6H5CO.C(OH)2C6H5  ->  (C6H5)2 :  C(OH)CO.OH. 

The  acid  can  also  be  obtained  directly  from  benzil  by  the  action  of  air 
and  caustic  potash. 

0+H20 

C6H5CH(OH)CO.C6H5  >  (C6H5)2C(OH)COOH. 

Anisil  and  cuminil  in  a  similar  way  yield  anisilic  and  cuminilic  acids. 
Preparation  47. — Benzilic  Acid  (Diphenyl-hydroxy-ethan  acid). 

(C6H5)2C(OH).COOH.  C14H1203.  228. 
50  gms.  (excess)  of  caustic  potash  are  melted  with  a  small  quantity  of 
water  in  a  silver,  nickel,  or  copper  crucible.  The  liquid  is  allowed  to  cool 
to  150°  (for  combined  thermometer  and  stirrer,  and  precautions  to  be 
taken  in  alkali  fusions,  see  Fig.  50),  and  10  gms.  of  dry,  finely  powdered 
benzil  are  added  with  constant  stirring.  The  benzil  melts  and  the  whole 
soon  sets  to  a  solid  mass  of  potassium  benzilate.  When  all  the  oil  has  dis- 
appeared, the  melt  is  cooled,  dissolved  in  water,  and  benzilic  acid  pre- 
cipitated by  acidifying  with  hydrochloric  acid.  The  precipitate  is  cooled 
with  cold  water  and,  to  free  it  from  traces  of  benzoic  acid,  is  boiled  in  a 


106  SYSTEMATIC  ORGANIC  CHEMISTRY 


dish  with  water  until  the  smell  of  the  latter  has  disappeared.  On  cooling, 
benzilic  acid  separates,  and  is  purified  by  recrystallisation  from  hot  water. 

C6H5CO.CO.C6H5  +  KOH  =  (C6H5)2C(OH)COOK. 

Yield.— 80%  theoretical  (16  gms.).    See  Preparation  48.    (A.,  25,  25  ; 
31,  329  ;  B.,  14,  316.) 
Peeparation  48. — Benzilic  Acid. 

(C6H5)2C(OH).COOH.       C14H1203.  228. 

20  gms.  (1  mol.)  of  benzil,  20  gms.  (excess)  of  solid  potassium  hydroxide, 
and  40  c.cs.  of  water  are  placed  in  a  flask,  and  when  the  potash  has  dissolved, 
50  c.cs.  of  alcohol  are  added.  The  mixture  is  then  boiled  for  10 — 12  minutes 
(not  longer)  on  a  boiling  water  bath  ;  poured  while  still  boiling  into  a 
beaker,  and  cooled  and  stirred  to  accelerate  crystallisation.  After  half 
an  hour's  standing  in  ice,  the  crystals  are  filtered  off  at  the  pump  through 
hardened  filter  paper,  well  pressed,  and  carefully  washed  with  4(> — 50  c.cs. 
of  ice-cold  alcohol,  so  that  the  filtrate  is  finally  almost  colourless.  The 
crystals  are  then  dissolved  in  about  400  c.cs.  of  water,  the  solution  filtered, 
brought  to  the  boiling  point,  and  20  c.cs.  of  boiling  dilute  sulphuric  acid  are 
added.  Part  of  the  benzilic  acid  precipitates  as  an  oil  which,  however, 
at  once  crystallises  ;  the  rest  separates  out  in  colourless  needles  on  cooling 
the  solution.    It  can  be  again  recrystallised  from  hot  water. 

C6H5.CO.CO.C6H5  +  KOH  =  (C6H5)2C(OH).COOK. 

Yield. — 90%  theoretical  (20  gms.).  Colourless  needles ;  scarcely 
soluble  in  cold  water  ;  readily  in  hot  water,  and  in  alcohol ;  M.P.  150°. 
(B.,  4,  1644.) 

Reaction  XXXIII.  (a)  Condensation  of  an  Aromatic  Carboxylic  Acid 
with  Formaldehyde.  (Lederer-Manasse). — In  the  presence  of  mineral  acids 
formaldehyde  condenses  to  di-phenyl  derivatives  with  aromatic  acids  in 
much  the  same  way  as  with  phenols  (Reaction  XIII.),  except  that  in  this 
case  it  is  in  the  meta  position  the  condensation  takes  place. 

Reaction  XXXIII.  (b)  Condensation  of  Malonic  Acids  with  Aldehydes 
or  some  Ketones  under  the  influence  of  Primary  or  Secondary  Amines. 
(B.,  35,  1143.) — This  is  an  example  of  the  activating  effect  of  two  1  :  3-oxy 
groups  on  a  methylene  group  between  them.  In  the  presence  of  primary  " 
or  secondary  amines  —  e.g.,  ethylamine,  di-ethylamine,  piperidine — 
malonic  acid  condenses  with  aldehydes  and  some  ketones  to  give  unsatu- 
rated dicarboxylic  acids.  It  is  probable  that  the  amine  reacts  first  with 
the  aldehyde,  water  being  eliminated. 

E.CHO  +  H^Rj  =  R.CH  :  NRj  +  H20, 

or 

E.CHO  +  2HNRn  =  R.CH  :  (NRn)2  +  H20. 
(R1]L  =  a  divalent  or  two  monovalent  radicals.) 

The  aldehyde  derivative  then  acts  on  the  acid  to  regenerate  the  amine, 
RCH  :  NRX  +  CH2(COOH)2  =  R.CH  :  C(COOH)2  +  NH^ 

or 

RCH(NRU)2  +  CH2(COOH)2  =  RCH  :  C(COOH)2  +  2NHRJJ. 


CAKBON  TO  CAKBON 


107 


In  this  way  cinnamic  aldehyde  and  malonic  acid  give  cinnamylidene 
malonic  acid. 

C6H5.CH  :  CH.CHO  +  H2C(COOH)2  =  C6H5CH  :  CH.CH  :  C(COOH)2  +  H20. 

This  latter,  like  all  malonic  acid  derivatives,  loses  carbon  dioxide  in 
heating,  and  yields  cinnamylidene  acetic  acid  (see  Preparation  426).  For 
another  and  similar  condensation  brought  about  by  amines,  see  Keaction 
XLV. 

Reaction  XXXIII.  (c)  Condensation  of  Aldehydes  with  Malonic  Acid  in 
the  presence  of  Alcoholic  Ammonia.  (B.,  31,  2604.) — When  aldehydes  are 
heated  on  a  water  bath  with  1  mol.  of  malonic  acid  and  2  mols.  of  dilute 
alcoholic  ammonia,  condensation  takes  place  as  in  the  previous  reaction, 
but  elimination  of  carbon  dioxide  simultaneously  occurs,  so  that  it  is  an 
unsaturated  derivative  of  acetic  acid  that  is  formed. 

NH3  CH2(COOH)2 

C6H5.CHO  >  C6H5.CH  :  NH  > 

C6H5CH  :  C(COONH4)2  ->  C6H5CH  :  CHCOONH4 
->C6H5CH  :  CHCOOH. 

In  this  way,  also,  crotonaldehyde  yields  sorbic  acid  (B.,  33,  2140). 

CH3.CH  :  CH.CHO  ->  CH3.CH  :  CH.CH  :  C(COO.H.)2 
->  CH3CH  :  CH.CH  :  CHCOOH. 

Preparation  49. — Cinnamic  Acid  (3-Phenyl-2-propen  acid). 

C6H5CH  :  CH.COOH.       C9H802.  148. 

20  gms.  (1  mol.)  of  benzaldehyde  and  80  gms.  (2  mols.  of  NH3)  of  an  8% 
solution  of  ammonia  in  alcohol,  are  added  to  20  gms.  (1  mol.)  of  malonic 
acid.  The  mixture  is  heated  on  a  water  bath  until  a  clear  solution  is 
obtained.  The  alcohol  is  then  removed  by  evaporation  and  the  heating 
continued  until  the  evolution  of  carbon  dioxide  ceases.  The  residue  is 
dissolved  in  water,  and  cinnamic  acid  precipitated  by  adding  hydrochloric 
acid.    It  is  then  purified  as  in  Preparation  50. 

C6H5CHO  +  H2C.(COOH)2^C6H5CH  :  CH.COOH  +  C02  +  H20. 

Yield.— 80%  theoretical  (22  gms.)  (see  p.  109).  (A.,  188,  194  ;  B.,  31, 
2604.) 

Reaction  XXXIII.  (d)  Condensation  of  Aldehydes  with  the  Sodium 
Salts  of  certain  Acids  in  the  presence  of  Acid  Anhydrides  (Perkin).  (A. 
100,  126  ;  227,  48  ;  B,  10,  68  ;  14,  1826  ;  J.  C.  S.,  21,  53  ;  J.,  1877,  789.) 
— This  is  a  reaction  of  very  wide  application,  and  one  much  used  in  the 
preparation  of  unsaturated  aromatic  carboxylic  acids.  It  consists  in 
heating  together — usually  to  180° — an  aldehyde,  the  sodium  salt  of  a 
fatty  acid  with  at  least  one  a-hydrogen  atom,  and  an  acid  anhydride.  The 
following  series  of  reactions  then  occur  : — 

(i.)  Condensation  takes  place  between  the  a-carbon  of  the  acid  salt  and 
the  aldehydic  carbon  (cf.  the  aldol  condensation,  p.  95). 

H.CUO  +  Rx.CH2.COONa  ->  R.CH(OH).CHR}.COONa, 


108  SYSTEMATIC  ORGANIC  CHEMISTRY 

The  hydroxy  acid  so  formed  is  stable  if  :  (a)  the  a-carbon  of  the  original 
acid  has  only  one  hydrogen  atom  attached,  e.g., 

C6H5.CHO  +  (CH3)2.CHCOONa  ->  C6H5CH(OH)C.(CH3)2COONa. 

or  (b)  it  is  a  a-hydroxy  acid,  and  so  immediately  forms  a  stable  lactone. 
This  occurs  when  sodium  succinate  is  employed. 

C6H5.CHO  +  CH2.COONa 

->  C6H5.CH.(OH).CH.(COONa).CH2.COONa. 

CH2COONa 

->  C6H6.CH(OH).CH(COOH).CHa.COOH  ->  C6H5.CH.CH(COOH) 

CH2 
I 

0 — CO 
Phenyl -par aconic  Acid. 

(ii.)  Except  in  the  above  cases,  elimination  of  water  occurs  and  an 
oc,  j8  unsaturated  acid  is  formed. 

E.CHCOHJ.CHEpCOONa  ->  E.CH  :  CE^COONa. 

(iii.)  If  an  or^o-phenolic  aldehyde  is  used,  a  further  loss  of  water  takes 
place  with  the  formation  of  a  lactone. 


/\CHO  /\CH  :  CH  /  \.CH  :  CH 

CH,COONa 


\/OH  \/0H  C00H     \/— 0— CO 

Although  the  anhydride  used  need  not  be  that  of  the  acid  of  which  the 
Na  salt  is  used,  it  is  best  to  have  it  so  ;  otherwise  there  is  a  Hability  to 
double  decomposition  between  the  sodium  salt  and  the  anhydride,  giving 
both  sodium  salts  and  both  anhydrides,  thus  leading  to  a  mixture  of  con- 
densation products.  A  low  temperature  helps  to  prevent  such  decom- 
position. 

Both  substituted  aldehydes  and  acids  may  be  used  so  that  the  reaction 
is  capable  of  numerous  modifications.  The  following  equations  will 
illustrate  this — 

C6H5CHO  +  CH2ClCOONa  — >  C6H5.CH  :  CC1.COOH. 

C.Hs.CH  :  CH.CHO  +  CH3COONa  ->  C6H5CH  :  CH.CH  :  CHCOOH. 


CH:CH.CH:CHC00H. 


H  C^^l      i  — —  0^^ 
2  \(>l     ICH:CH.CHO  +  CH3COONa  ->  CH2    I  I 

 0\/ 

Piperic  Acid. 

A.Uphatic  aldehydes  may  also  be  used  in  this  reaction,  but  react  with 
difficulty. 


C ABB ON  TO  CARBON 


109 


h  '  Pkeparation  50. — Cinnamic  Acid  (3-Phenyl-2-propen  acid). 

C6H5.CH  :  CH.COOH.       C9H802.  148. 

[  20  gms.  (excess)  of  benzaldehyde,  30  gms.  (excess)  of  acetic  anhydride 
both  freshly  distilled,  and  10  gms.  (1  mol.)  of  freshly  prepared  powdered 
anhydrous  sodium  acetate  (see  p.  506)  are  refluxed  together  for  8  hours 
in  a  250  c.c.  round-bottomed  flask  fitted  with  a  wide  vertical  air-con- 
denser about  60  cms.  long  in  an  oil  bath,  kept  at  180°.  A  calcium  chloride 
tube  is  fitted  to  the  top  of  the  condenser.  The  experiment  need  not  be 
completed  in  1  day  ;  when  finished,  the  hot  reaction  mixture  is  poured 
into  a  1 -litre  round-bottomed  flask,  sodium  carbonate  is  added  till  alkaline, 
and  then  water  until  the  bulk  is  5  times  the  original.  The  whole  is  then 
steam-distilled  until  no  more  benzaldehyde  comes  over.  The  residue  is 
filtered  hot  through  a  wet,  folded  filter  paper  to  remove  oil  and  resinous 
by-products  ;  cooled,  and  acidified  with  dilute  hydrochloric  acid.  The 
precipitated  cinnamic  acid  is  purified  by  reprecipitation  from  alkaline 
solution  or  by  recrystallisation  from  hot  water. 

C6H5.CH  :  0  +  CH3.COONa  ->  C6H5.CH(OH).CH2.COONa  -> 
C6H5.CH  :  CH.COONa  ->  C6H5.CH  :  CH.COOH. 

7  Yield.— 85%  theoretical  (15  gms.).  Crystallises  from  hot  water  in  fine 
needles  ;  from  alcohol  in  thick  prisms  ;  readily  soluble  in  hot  water  ; 
M.P.  133°  ;  B.P.  760  3  00°.     (A.,  227,  48  ;  J.  C.  S.,  21,  53  ;  B.,  16,  1436.) 

Malonic  acid  condenses  especially  readily.    Even  at  ordinary  tem- 
peratures, in  presence  of  acetic  anhydride,  it  yields  benzalmalonic  acid 
.  with  benzaldehyde.    Better  results  are  obtained,  however,  by  using  a  less 
powerful  condensing  agent — glacial  acetic  acid — at  100°.    This  synthesis 
is  interesting  as  providing  a  method  for  the  preparation  of  certain  mono- 
basic acids,  since  all  malonic  acids  readily  lose  carbon  dioxide  on  heating 
(see  Preparation  426). 
Preparation  51. — Benzalmalonic  acid  (2-Benzylidene-propan-di-Acid). 

C6H5CH  :  C(COOH)2.       C10H8O4.  192. 

4  gms.  of  glacial  acetic  acid,  7  gms.  (1  mol.)  of  benzaldehyde  and  7  gms 
J[l  mol.)  of  malonic  acid  are  heated  together  for  10  hours  at  100°  under  a 
reflux.    On  cooling,  benzalmalonic  acid  separates  out,  is  filtered  off  and 
washed  with  chloroform. 

C6H5CHO  +  H2C(COOH)2  ->  C6H5CH  :  C(COOH)2  +  H20. 

i  Yield.— 40  %  theoretical  (5—6  gms.).  Colourless  crystals  ;  M.P.  196° 
with  decomposition  ;  insoluble  in  chloroform  ;  is  converted  to  cinnamic 
acid  at  200°— 210°.    (A.,  218,  129.) 

Reaction  XXXIII.  (e)  Condensation  of  the  Dichlorides  of  Aromatic 
Aldehydes  with  the  Sodium  Salts  of  certain  Acids.  (B.,  15,  969.) — This  is 
a  modification  of  the  previous  reaction  used  commercially  to  prepare 
cinnamic  acid,  by  heating  sodium  acetate  with  benzal  chloride.  The 

l  latter  is  much  cheaper  than  benzaldehyde. 

C6H5.CHC12  +  CH3.COONa  =  C6H5.CH :  CH.COONa  +  NaCl  +  HC1. 


110  SYSTEMATIC  ORGANIC  CHEMISTRY 


Reaction  XXXIV.    (a)  Condensation  of  Carbon  Dioxide  with  a  Phenol 

(Kolbe  and  Schmitt).  (J.  pr.5  [2]  10,  89  ;  27,  39  ;  31,  397.)— When 
carbon  dioxide  is  passed  over  dry  sodium  phenolate  at  110°,  sodium 
phenylcarbonate  is  obtained. 

C6H5ONa  +  C02  =  C6H5O.CO.ONa. 

If  the  temperature  be  then  slowly  raised  to  190°,  intramolecular 
rearrangement  takes  place,  and  monosodium  salicylate  is  formed.  This, 
at  ordinary  pressures  reacts  with  unchanged  sodium  phenolate  to  produce 
di-sodium  salicylate  and  phenol. 

/^O.CO.ONa  f^011 
[^J  ^/COONa. 
C6H4(OH)(COONa)  +  C6H5ONa  =  C6H4(ONa)(COONa)  +  C6H5OH 

This  is  "  Kolbe's  synthesis  "  of  phenoHc  acids.  It  is  capable  of  very 
wide  application.  In  all  cases  the  carboxyl  group  primarily  seeks  the 
ortho-position  ;  if  that  is  occupied,  some  condensation  in  the  para-position 
occurs.    The  following  are  some  examples. 

(i.)  Phenolic  ethers  also  react,  e.g.,  sodium  guaiocolate  gives  3-methoxy- 
2-hydroxy-benzoic  acid. 

(ii.)  The  polyhydric  phenols  react  especially  easily.  Boiling  with  an 
aqueous  solution  of  ammonium  carbonate  or  under  pressure  with  aqueous 
potassium  carbonate  is  sufficient.    (M.,  1,  236,  468  ;  2,  448,  458.) 

C6H4(OH)2  +  OH.COOK  =  C6H3(OH)2COOK  +  H20. 

(iii.)  oc-  and  j8-naphthols  yield  each  a  hydroxy-naphthoic  acid. 

It  is  an  interesting  fact  that  if  potassium  phenolate  is  used  in  the  Kolbe 
synthesis  para-hydroxy  benzoic  acid  is  obtained,  especially  at  high  tem- 
peratures. Potassium  phenyl  carbonate  is  first  formed,  and  heated  up  to 
150°  yields  salicjdic  acid,  but  if  the  temperature  be  further  raised,  the 
para-acid  is  produced  in  increasing  quantities  until  at  220°  potassium  jpara- 
hydroxy-benzoic  acid  is  the  sole  product. 

It  will  have  been  noted  that  in  the  formation  of  salicylic  acid,  only  onev 
half  of  the  phenol  is  converted  ;  the  rest  is  obtained  unchanged.  Schmitt 
(Dingier 's  Polytechnisches  Journal,  255,  259)  succeeded  in  modifying  the 
synthesis  to  obviate  this  defect,  and  his  is  the  method  always  used  in- 
dustrially, although  the  other  is  more  convenient  in  the  laboratory.  In 
Schmitt's  synthesis  sodium  phenyl  carbonate  is  prepared  by  heating  up 
to  120° — 140°  dry  sodium  phenolate  with  carbon  dioxide  in  autoclaves 
under  pressure.  Complete  transformation  of  the  sodium  phenyl  carbonate 
first  formed  to  mono-sodium  salicylate  then  occurs  on  further  heating. 
The  carbon  dioxide  may  be  led  in  from  a  cylinder  under  pressure,  or 
liquid  or  solid  carbon  dioxide  may  be  mixed  directly  with  the  sodium 
phenolate  in  the  autoclave.  If  preferred,  the  sodium  phenyl  carbonate 
can  be  prepared  at  ordinary  pressures  at  110°  and  then  heated  under 
pressure  at  140°. 


CAEBON  TO  CARBON 


111 


Preparation  52. — Salicylic  Acid  (l-Hydroxy-2-carboxy-benzene). 

.OH 

/\C0.0H. 

I     J  C7H603.  138. 

(Kolbe's  Method.) 

1  10  gms.  (2  mols.)  of  pure  sodium  hydroxide  are  dissolved  in  15  c.cs.  of 
water  in  a  metal  basin,  and  with  stirring,  23  gms.  (2  mols.)  of  crystallised 
phenol  are  gradually  added.  The  solution  is  then  heated  over  a  small 
tree  flame,  with  continual  stirring,  until  a  crystalline  film  forms  on  the 
surface  of  the  liquid.  Evaporation  is  continued  by  heating  with  a 
luminous  flame  kept  in  constant  motion.  During  the  process  the  basin 
should  be  securely  clamped.  A  caked  mass  is  obtained  which  is  crushed 
at  intervals  with  a  pestle.  When  the  mass  no  longer  cakes  together,  it  is 
transferred  to  a  dry  warm  mortar  and  pulverised  as  it  cools.  The  powder 
while  still  warm,  is  quickly  returned  to  the  basin,  and  heated  as  before 
with  thorough  stirring,  until  it  is  dry  enough  to  form  dust.  It  is  then 
immediately  placed  in  a  200-c.c.  tubulated  retort,  where  it  is  heated  in  a 
bath  to  140°  in  a  fairly  rapid  current  of  dry  hydrogen  (caution)  obtained 
from  a  Kipp  generator. 

*  When  in  about  1  hour  no  more  moisture  condenses  in  the  neck  of  the 
retort,  and  the  body  of  the  retort  appears  dry,  the  mass  is  allowed  to  cool 
in  the  current  of  hydrogen  and  then,  while  still  warm,  broken  up,  removed, 
quickly  powdered  in  a  mortar  and  replaced.  The  object  of  the  above 
operations  is  to  obtain  perfectly  dry,  uncharred,  well  powdered  sodium 
phenate,  for  it  is  on  these  factors  that  the  success  of  the  whole  preparation 
depends.    A  moderate  stream  of  carbon  dioxide,  dried  through  two  wash 

f  bottles  of  cone,  sulphuric  acid  is  passed  over  the  surface  of  the  sodium 
phenate  by  means  of  a  bent  tube  fixed  through  the  tubulus  of  the  retort, 
and  terminating  1  cm.  above  the  substance.  The  retort  is  immersed  as 
far  as  possible  in  the  oil  bath,  and  the  temperature  gradually  raised  to 

-  110°  and  kept  there  for  1  hour.  The  temperature  is  then  raised  to  190°  in 
4  hours,  and  on  to  200°,  where  it  is  kept  for  2  hours.  During  the  whole 
operation,  the  mass  is  stirred  frequently  with  a  glass  rod  momentarily 

P  inserted  through  the  tubulus,  and  the  retort  also  shaken  from  time  to  time, 
to  ensure  that  fresh  surfaces  shall  be  exposed  to  the  action  of  the  gas. 
During  the  heating  phenol  distils  and  collects  in  the  neck  of  the  retort 
while  the  contents  darken  in  colour.    On  cooling,  the  phenol  is  melted  by 

^  application  of  a  flame  to  the  outside  of  the  neck  and  allowed  to  flow  away  ; 
then  the  crude  reaction  product  is  shaken  out  through  the  tubulus  into  a 
large  beaker,  and  the  retort  washed  out  several  times  with  warm  water. 
The  whole  is  boiled,  filtered  if  necessary,  and  treated  with  much  cone, 
hydrochloric  acid  (100  c.cs.),  cooled  for  some  hours  in  ice-water,  and  pre- 
cipitation of  the  crude  salicylic  acid  facilitated  by  rubbing  the  sides  of  the 
vessel  with  a  glass  rod.    The  precipitate  is  filtered  off  at  the  pump,  washed 

\  with  a  little  cold  water,  and  dried  on  a  porous  plate.  The  filtrate  is  eva- 
porated to  low  bulk,  and  a  little  more  acid  obtained.    It  may  be  purified 


112 


SYSTEMATIC  OKGANIC  CHEMISTRY 


by  recrystallising  from  boiling  water  with  the  addition  of  animal  charcoal, 
but  it  is  better  to  distil  the  crude  acid  with  superheated  steam  (see 
p.  23).    The  crystals  are  thoroughly  dried,  first  on  a  porous  plate,  and 
then  by  heating  on  a  water  bath.    They  are  placed  in  a  short-necked  flask  ^ 
and  heated  in  an  oil  bath  to  170°.    Then  connection  is  made  to  the  steam 
generator  and  a  moderate  current  of  steam  at  175°  pressed  in.    It  is  I 
important  that  the  steam  generator  be  not  connected  to  the  flask  till  the 
oil  bath  and  steam  have  the  same  temperature.    A  wide  condenser  is  % 
used  (width  of  inner  tube  3  cms.  ;  of  outer  jacket  6  cms.  ;  length  of  latter 
80  cms.),  otherwise  the  condensing  acid  soon  blocks  it.    The  connecting 
tube  between  the  flask  and  condenser  must  be  2-5  cms.  wide,  and  as  short 
as  possible.    The  side-piece  should  be  near  the  bulb.    When  no  more  acid 
distils,  the  crystals  in  the  condenser  are  added  to  the  distillate  which  is  1 
boiled  and  filtered.    The  acid  separates  on  cooling. 

C6H5.O.Na  +  C02  =  C6H5O.CO.ONa. 

^ONa 

C6H5O.CO.ONa  +  C6H5ONa  =  C6H3  +  C6H5OH. 

^CO.ONa 

•  "I 

Yield. — 60%  theoretical,  allowing  for  phenol  recovered  (10  gms.) 
Colourless  needles  ;  soluble  in  alcohol  and  hot  water  ;  much  used  in  w. 
industry  as  an  antiseptic  and  a  dye  intermediate ;  like  all  or^o-hydroxy 
benzoic  acids,  is  volatile  in  steam  (cf.  Preparation  43) ;  yields  phenol 
on  heating  ;  M.P.  158'5°.  (B.,  8,  537  ;  Dingl.  Poly.  J.,  (1885),  255,  259  ; 
D.R.P.,  38,  742  ;  E.P.,  7801/86.)    (J.  pr.,  [2],  10,  95  ;  27,  39  ;  31,  397.) 

Reaction  XXXIV.    (6)  Action  of  Carbon  Dioxide  on  an  Organo-mag-  I 
nesium  Halide  (Grignard).    (B.,  35,  2519  ;  39,  634  ;  40,  1584.)— When 
an  alkyl  or  aryl  magnesium  bromide  or  iodide  dissolved  in  dry  ether  is 
treated  with  dry  carbon  dioxide,  the  mono-carboxylic  acid  of  the  next  9 
higher  series  is  formed.    Like  all  "  Grignards  "  (see  pp.  61,  67,  89)  this 
reaction  is  of  very  general  application.    It  works  better  with  iodides  than 
with  bromides,  and  with  aryl  rather  than  alkyl  compounds.    The  general 
remarks  on  the  other  Grignard  reactions  apply  here.    Moisture  must  be  ■ 
absent,  iodine  can  be  used  as  a  catalyst  and  so  on.    Also  the  reaction  takes 
place  in  two  stages,  the  usual  intermediate  compound  being  obtained. 

R.Mg.I  +  C02  =  K.COOMgl. 
E.COOMgl  +  H20  =  R.COOH  +  OH.Mgl. 

Either  acid  or  alkali  can  be  used  to  hydrolyse  the  intermediate  com- 
pound. The  yields  in  most  cases  are  good,  but  the  reaction  can  sometimes 
take  another  course.    (B.,  40,  1584.) 

Before  the  following  preparations  are  attempted,  the  methods  for  the 
three  should  be  studied  and  compared. 

Preparation  53. — Propionic  Acid  (propan  acid). 

CH3.CH2.COOH.       C3H602.  74. 

All  vessels  used  in  this  experiment  must  be  absolutely  dry.    12  gms.  . 
(1  mol.)  of  dry  bright  magnesium  turnings  (see  Preparation  18)  are  dis- 


CARBON  TO  CARBON 


113 


solved  in  a  solution  of  28  gms.  (1  mol.)  of  dry  ethyl  iodide  in  20  c.cs.  of  dry 
ether  (see  p.  209)  contained  in  a  flask  fitted  with  a  reflux  condenser. 
The  action  may,  if  necessary,  be  started  by  adding  a  crystal  (0-05  gm.)  of 
iodine  ;  should  it  become  too  vigorous,  it  is  moderated  by  cooling  in 
water.  When  all  the  magnesium  has  dissolved,  a  not  too  rapid  stream  of 
carbon  dioxide,  washed  once  with  sodium  carbonate  solution,  twice  with 
cone,  sulphuric  acid,  and  passed  then  over  phosphorus  pentoxide,  is  led 
in  until  it  ceases  to  be  absorbed,  the  flask  being  cooled  if  required.  The 
ether  is  removed  on  a  water  bath  and  the  residue  distilled  with  dilute 
sulphuric  acid  (water  is  added  as  required)  until  the  distillate  is  no  longer 
acid.  The  propionic  acid  may  be  isolated  by  forming  the  lead  salt,  pro- 
ceeding as  in  Preparation  473,  or  the  aqueous  solution  may  be  treated 
with  excess  of  sodium  carbonate  and  evaporated  to  dryness.  The 
powdered  residue  is  then  distilled  with  cone,  sulphuric  acid  until  the 
temperature  reaches  155°.  The  distillate  is  again  distilled,  the  fraction 
137° — 142°  being  retained. 

C2H5I  +  Mg  =  CaH5.Mg.I. 
C2H5.Mg.I  +  C02  =  C2H5.COOMgI. 
C2H5.CO.OMgI  +  H20  =  C2H5.COOH  +  (OH)MgL 

Yield. — 50%  theoretical  (7  gms.).  Colourless  liquid ;  rancid  acid 
odour  ;  M.P.  24°  ;  B.P.  141°  ;  D.  J 1-013. 

How  the  yield  increases  with  aryl-compounds  may  be  seen  from  the  two 
following  preparations. 

Preparation  54. — Benzoic  Acid  (Benzene-mono-carboxylic  acid). 

C6H5.COOH.       C7H602.  122. 

2-6  gms.  (1  mol.)  of  clean  magnesium  powder  (or  thin  shavings  or  ribbon 
about  2  mms.  in  width,  each  piece  about  1  cm.  long,  cleaned  with  fine 
emery  paper  and  then  with  filter  paper)  are  dried  in  an  air  oven  at  110°  for 
20  minutes  and  placed  in  a  dry  flask  fitted  with  a  reflux.  A  mixture  of 
40  c.cs.  of  dry  ether  (see  p.  209)  and  20-4  gms.  (1  mol.)  of  dry  iodo- 
benzene  of  constant  boiling  point,  and  a  crystal  of  iodine  are  then  added. 
The  flask  is  dipped  in  hot  water  or  heated  on  a  water  bath  so  that  the  ether 
boils  gently. 

In  about  half  an  hour  a  white  flocculent  precipitate  will  begin  to  form, 
and  when  the  heat  of  the  reaction  makes  the  ether  boil  vigorously,  the 
water  bath  is  removed.  The  flask  is  now  wrapped  in  a  dry  cloth  to  con- 
serve the  heat  of  the  reaction,  and  in  the  course  of  2  hours  the  magnesium 
'will  have  practically  all  dissolved.  (If  this  does  not  occur,  traces  of 
moisture  are  present,  and  the  experiment  must  be  repeated,  the  ether 
being  distilled  off  and  again  dried  over  sodium.)  When  the  boiling  of  the 
ether  slackens,  the  flask  is  reheated  for  half  an  hour  as  before  on  a  water 
♦  bath. 

The  flask  is  then  cooled  in  ice-water,  the  condenser  removed,  and  a  slow 
current  of  carbon  dioxide,  washed  and  dried  as  in  the  previous  experiment, 
'  is  led  into  the  ethereal  solution,  which  may  still  contain  traces  of  undis- 
solved magnesium.    The  cooling  must  be  continued  throughout  the 
s.o.c.  i 


114  SYSTEMATIC  ORGANIC  CHEMISTRY 


operation.  The  reaction  mixture  forms  two  layers,  an  upper  layer  of 
ether,  and  a  heavy  resinous  lower  layer  of  the  reaction  product.  If  the 
gas  current  is  too  rapid,  only  a  slight  layer  of  resinous  mass  will  be  obtained, 
but  the  preparation  will  still  succeed  if  the  cooling  be  thorough.  Pow- 
dered ice  is  now  added,  and  then,  slowly,  30  c.cs.  (excess)  hydrochloric 
acid  (1  :  1).  The  precipitated  benzoic  acid  is  extracted  with  ordinary 
ether,  the  latter  removed  on  a  water  bath,  and  the  residue  gently  warmed 
with  dilute  caustic  alkali.  The  undissolved  portion  (see  B.,  49,  1584)  is 
filtered  off,  and  the  benzoic  acid  reprecipitated  with  hydrochloric  acid. 
More  acid  is  obtained  by  extracting  the  mother  liquor  with  ether.  The 
whole  is  recrystallised  from  hot  water. 

C6H5I  ->  CsH5.Mg.I  ->  C6H5.CO.O.MgI  ->  C6H5.COOH. 

Yield. — 90%  theoretical  (11  gms.).  Colourless  needles  ;  soluble  in  hot 
water,  and  in  alcohol  and  ether  ;  volatile  in  steam  ;  M.P.  122°  ;  B.P.  250°. 
(B,  38,  2759.) 

C02  can  also  be  added  directly  to  benzene  in  presence  of  aluminium 
chloride  to  yield  benzoic  acid. 
Pkeparation  55. — Triphenylacetic  Acid  (Triphenylethan  acid). 

(C6H5)3C.COOH.       C20H16O2.  288. 

10  gms.  (1  mol.)  of  triphenyl  chloromethane  (see  p.  425)  and  0-05 — 
0-1  gm.  of  iodine,  are  dissolved  by  gentle  heating  in  50  c.cs.  of  ether,  dried 
as  on  p.  209.  2  gms.  (2 \  mols.)  of  clean,  dry  magnesium  powder  (see 
Preparation  18),  are  added,  and  the  whole  boiled  under  a  reflux  while 
a  not  too  rapid  current  of  dry  carbon  dioxide  (see  Preparation  52)  is  led 
into  the  liquid.  After  3  hours,  a  lemon-yellow  precipitate  of  the  complex 
magnesium  compound  has  formed.  While  the  carbon  dioxide  is  passing 
in,  the  whole  is  frequently  shaken  up,  and  dry  ether  is  added  to  replace 
that  removed  by  the  carbon  dioxide.  To  decompose  the  complex  mag- 
nesium compound,  60  c.cs.  of  water  are  added  to  the  flask,  and  the  whole 
well  shaken,  poured  into  a  basin,  gradually  treated  with  40  c.cs.  of  cone, 
hydrochloric  acid  to  dissolve  the  excess  of  magnesium,  and  boiled  for 
3  minutes,  during  which  it  is  well  shaken.  The  crude  acid  is  filtered  off 
on  cooling,  washed  and  boiled  in  a  porcelain  basin  with  200  c.cs.  (excess)  of 
a  10%  caustic  soda  solution  and  100  c.cs.  of  water,  when  the  greater  portion 
of  the  acid  goes  into  solution.  The  mixture  is  diluted  with  300  c.cs.  of 
water,  cooled,  filtered,  and  100  c.cs.  of  cone,  hydrochloric  acid  added.  The 
liquid  is  heated  to  make  the  somewhat  gelatinous  precipitate  granular,  j 
cooled,  the  acid  filtered  off,  washed  and  dried.  It  is  recrystallised  from 
glacial  acetic  acid. 

(C6H5)3CC1  ->  (C6H5)3CMgCl  ->  (C6H5)3CCOOMgCl  ->  (C6H5)3C.COOH. 

Yield. — 83%  theoretical  (8-5  gms.).  Long  glittering  prisms  ;  sparingly 
soluble  in  water,  ether  or  benzene  ;  M.P.  264°— 265°.    (B.,  39,  634.) 

For  a  resume  of  some  recent  applications  of  the  Grignard  reagents,  see 
J.  S.  C.  L,  41,  7. 


CARBON  TO  CARBON 


115 


Reaction  XXXIV.  (c)  Action  of  Carbon  Dioxide  on  Sodium  Acetylides 
in  Dry  Ether.  (B.,  12,  853  ;  J.  pr.,  [2],  27,  417  ;  B.,  33,  3586.)— This  is  an 
example  of  the  great  activating  influence  of  a  triple  bond,  When  carbon 
dioxide  is  passed  into  a  solution  of  the  sodium  derivative  of  an  acetylenic 
hydrocarbon  in  dry  ether,  direct  addition  takes  place  to  give  the  sodium 
salt  of  the  next  highest  acetylenic  carboxylic  acid.  For  example,  sodium 
allylene  yields  sodium  tetrolate — 

CH3C  :  CNa-^CH.3.C  ;  C.COONa, 

and  sodium  phenyl-acetylene  gives  sodium  phenyl-propiolate — 

C6H5C  ;  CNa->C6H5.C  :  C.COONa. 

This  reaction  should  be  compared  with  the  preceding  one.  The  fact 
that  the  presence  of  a  triple  bond  attached  to  a  carbon  makes  a  hydrogen 
attached  to  that  carbon  replaceable  by  a  metal  should  also  be  noted  (cf. 
Reaction  XXIII.  (a) ). 

Reaction  XXXV.  (a)  Condensation  of  Phthalic  Anhydride  with  Aro- 
matic Hydrocarbons  in  the  presence  of  Anhydrous  Aluminium  Chloride 
(Friedel-Crafts).  (A.,  291,  9  ;  C.  r.,  119,  139.)— When  the  dichloride  of 
phthalic  anhydride  reacts  with  an  aromatic  hydrocarbon  in  presence  of 
anhydrous  aluminium  chloride,  phthalophenone  (diphenylphthalide)  is 
formed  (see  p.  101).  With  phthalic  anhydride  itself  the  reaction  can  be 
made  to  take  the  same  or  a  different  course.  Using  an  excess  of  hydro- 
carbon, condensation  and  hydrolysis  occurs,  and  o-benzoyl-benzoic  acid 
or  its  homologues  are  obtained  according  to  the  reacting  hydrocarbon. 
Not  only  can  the  latter  be  varied,  but  derivatives  of  phthalic  anhydride 
may  be  used,  so  that  a  great  number  of  compounds  can  be  synthesised  in 
thislway. 

/COx  A1C13 
C6H4<^\0  +C6H6  > 

/CO.C6H5         H20  yCOC6H5 

C6H4<   >  C6H4< 

XJ0.0H(A1C13)  XIOOH. 

The  or^o-benzoyl-benzoic  acids  readily  yield  anthraquinone  and  its 
derivatives  (see  p.  77).  It  may  be  noted  that  o-benzoyl-benzoic  acid 
itself,  with  benzene  and  aluminium  chloride,  yields  phthalophenone  ;  the 
same  compound  is  made  directly  from  phthalic  anhydride  by  increasing 
the  amount  of  the  latter  or  by  adding  acetic  anhydride.  The  same  holds 
for  ^>-toluoyl-benzoic  acid  and  ditolylphthalide.  (Am.  Soc,  43,  1965  ; 
J.  C.  S.,  122,  539.)  (For  the  use  of  carbomethoxylbenzoyl  chlorides  and  of 
homophthalic  anhydrides  in  these  reactions,  see  Am.  Soc,  43,  1950.) 

Preparation  56. — o-Benzoyl-benzoic  Acid. 

yCOC6H5  [1] 
C6H4<  C14H10O3.  226. 

xCOOH  [2] 

175  gms.  (excess)  of  dry  benzene  are  added  to  50  gms.  (1  mol.)  of  finely 
powdered  phthalic  anhydride.    To  this  is  added  90  gms.  fresh  aluminium 

1  2 


116  SYSTEMATIC  ORGANIC  CHEMISTRY 


chloride  and  the  mixture  is  gently  heated  on  a  water  bath  in  a  flask  fitted 
with  a  good  mechanical  agitator  and  a  reflux  condenser  (see  Fig.  37). 
The  reaction  is  moderated  by  cooling.  When  the  mass  becomes  viscous, 
the  temperature  is  raised  to  7 0°  and  kept  there  till  the  evolution  of  hydro- 
chloric acid  ceases.  The  mechanical  agitator  is  removed  and  an  ordinary 
condenser  attached.  Four  volumes  of  cold  water  are  gradually  added 
through  ,a  tap  funnel,  and  the  heat  evolved  causes  most  of  the  unchanged 
benzene  to  distil  over.  Steam  is  then  passed  through  the  mixture  to 
remove  the  remainder  of  the  benzene,  and  the  residue  is  boiled  for  4  hours, 
caustic  soda  solution  being  added  to  make  slightly  alkaline.  The  pre- 
cipitated alumina,  formed  by  the  decomposition  of  the  aluminium  com- 
pound, is  filtered  off  and  washed  with  boiling  water.  The  filtrate  which 
contains  the  sodium  salt  of  o-benzoyl-benzoic  acid  is  then  acidified  with 
dilute  hydrochloric  acid,  and  the  free  acid  filtered  off.  It  is  then  recrystal- 
lised  from  water. 

/COv                  A1C13  .CO— C6H5 

C6H4<      >0  +  C6H6  >  C6H4< 

Yield.— 95%  theoretical  (72  gms.).  Colourless  crystals;  M.P.  127° 
when  anhydrous  ;  contains  1H20  when  crystallised  from  water  ;  M.P.  94°. 
(A.,  291,  9  ;  B.,  14,  1865  ;  41,  3631.) 

Peepakation  57.— 2-^-Toluoyl-benzoic  Acid  ( (2-Carboxyl-phenyl)- 
(4-methyl-phenyl)-methanon) . 

/\COOH  /\CH3. 

C15H1203.  240. 

— CO— 


50  gms.  (1  mol.)  of  finely  powdered  phthalic  anhydride  and  200  gms. 
(excess)  of  dry  redistilled  toluene  are  mixed  together,  and  100  gms.  (excess) 
of  finely  powdered,  freshly  prepared,  anhydrous  aluminium  chloride  (see 
p.  503)  are  added  all  at  once.  Hydrogen  chloride  is  evolved,  and  the 
mixture  becomes  warm.  After  10  hours,  water  is  added,  and  excess  of 
toluene  removed  by  steam-distillation.  The  aqueous  solution  is  poured 
off  (from  it  a  little  phthalic  acid  may  be  removed  by  acidification),  and  the 
remaining  cake  is  treated  with  sodium  carbonate  till  alkaline,  steam  is 
passed  in  for  5  hours  to  decompose  the  aluminium  compound,  the  whole 
filtered,  and  the  filtrate  acidified  whereby  [2-j9-toluoyl-benzoic  acid  is 
precipitated. 

.CO.  AICI3  /C6H4CH3 

C6H4<      >0  +  C6H5.CH3  >  C6H4< 

\C(K  \COOH(AlCl3) 
/C6H4.CH3 

->  c6h4<; 

X!OOH. 

Yield, — 97%  theoretical  (78  gms.).  Colourless  crystals  ;  insoluble  in 
cold  water  ;  M.P.  146°.  (B.,  41,  3632  ;  J.  pr.,  [2],  33,  318  ;  A.,  311, 
178.) 


CARBON  TO  CARBON 


117 


Reaction  XXXV.  (b)  Condensation  of  Phthalic  Anhydride  with  Phenols 
in  the  presence  of  Anhydrous  Aluminium  Chloride,  s-tetrachloroethane 
being  used  as  a  Solvent.  (B.,  52,  2098  ;  53,  826.)— This  is  an  extension  of 
the  previous  reaction  to  phenols;  employment  of  tetrachloroethane  as 
solvent  has  enabled  satisfactory  yields  to  be  obtained.  Condensation 
takes  place  in  the  or^o-position  to  the  hydroxyl  group.  Thus  phenol  and 
phthalic  anhydride  yield  2-(o-hydroxy-benzoyl)-benzoic  acid. 

OH 


A1C13  .CO  /\ 


C^XO+CAOH-  ->C6H4Xcooh 


and  j9-chloro-phenol  and  phthalic  anhydride  give  2-(2-hydroxy-5-chlor- 
benzovl)-benzoic  acid. 

OH 

/COx  AICI3         /CO  /\ 

C6H4<      >0  +  C1C6H40H  >  C6H4< 

X!(K  \COOH 


CI. 

This  reaction  is  especially  interesting  for  many  of  the  above  compounds 
readily  yield  the  corresponding  anthraquinone  derivatives  (see  p.  77), 
e.g.,  4-chloro-l-hydroxy-anthraquinone  has  been  obtained  from  j9-chloro- 
phenol ;  substituted  anthraquinones  of  this  type  are  becoming  increasingly 
important. 

Reaction  XXXVI.— Condensation  of  Carbon  Tetrachloride  with  Phenols 
and  simultaneous  Hydrolysis  (Tiemann-Reimer).  (B.,  10,  2185.) — This 
reaction  is  perfectly  analogous  to  that  of  the  formation  of  hydroxy- 
aldehydes  by  means  of  chloroform  and  caustic  alkali  (see  p.  98). 
A  mixture  of  a  phenol,  carbon  tetrachloride  and  caustic  soda  or  caustic 
potash  solution  are  boiled  together.  Condensation  occurs,  chiefly  in  the 
^am-position,  but  small  amounts  of  the  ortho-acids  are  also  formed.  The 
product  after  the  excess  of  carbon  tetrachloride  has  been  removed,  is 
saturated  with  carbon  dioxide  and  the  unchanged  phenol  extracted  with 
ether.  The  hydroxy  acids  are  then  precipitated  by  acidification  with 
hydrochloric  acid. 

/OH 

C6H5OH  +  CC14  -f  5KOH  =  C6H4<  +  4KC1  +  3H20. 

-COOK 

A  variation  of  this  method  consists  in  heating  carbon  tetrachloride  with 
potassium  phenolate  under  pressure  with  sufficient  alcohol  to  give  a  clear 
solution.  The  product  in  this  case  is  mostly  the  or^o-acid  (cf.  Reaction 
XXXIV.  {a) ). 

Reaction  XXXVII. — Action  of  finely  divided  Metals  on  Halogen  Acids. 

(B.,  2,  720  ;  28,  R.,  466.) — The  use  of  metals — sodium,  copper,  silver — to 
eliminate  halogen  from  halogen  compounds,  and  bring  about  the  con- 
densation of  the  carbons  to  which  the  halogen  atoms  are  attached  has,  as 
is  well  known,  a  very  wide  application.    It  is  employed  as  a  standard 


118  SYSTEMATIC  ORGANIC  CHEMISTRY 


method  with  the  halogen  acids  which  react  readily,  to  obtain  many 
of  the  higher  dibasic  acids.  Thus  bromacetic  acid  on  heating  with 
finely  divided  metallic  silver  yields  succinic  acid  ;  /3-iodo-propionic  acid 
in  a  similar  manner  gives  adipic  acid  with  silver  at  140°  and  with  copper 
at  160°. 


Ag2 


Br.CH2.COOH 
+ 


2AgBr  + 


Br.CH2.COOH 
I.CH2.CH2.COOH 
+ 

Ag2  ->  2AgI 

LCH2.CH2.COOH 


CH9.C00H 


CH2.COOH. 
CH2.CH2.COOH 


CH9.CH2.C00H. 


Of  the  metals  mentioned  silver  gives  the  best  results,  while  iodo-  and 
then  bromo-  give  better  yields  than  chloro-acids. 

This  synthesis  has  one  rather  anomalous  application,  when  a-brom- 
isobutyric  acid  (or  its  ethyl  ester)  is  heated  with  silver,  some  tetramethyl- 
succinic  acid  is  produced  in  the  ordinary  way  (B.,  23,  297  ;  26,  1458). 
But  there  also  appears  trimethylglutaric  acid  (A.,  292,  220  ;  C.  (1906),  II., 
422).  To  explain  the  unexpected  formation  of  this  acid,  it  has  been 
assumed  that  a  portion  of  the  a-bromisobutyric  acid  gives  up  HBr  to  form 
methacrylic  acid.  This  latter  then  forms  /3-bromisobutyric  acid,  and  the 
silver  withdraws  bromine  from  the  a-  and  acids,  whereby  the  residues 
unite  to  tri-methylglutaric  acid  (B.,  22,  48,  60).  A  similar  explanation 
applies  to  some  other  syntheses  in  which  tetramethylsuccinic  and  tri- 
methylglutaric acids  appear  together. 


HOOC.C(Br.; 


CH< 


CH2Br 


HBr 


CH,Br. 


>HOOC.CC  +  HBr  HOOC.CH< 

\CH3  ~         >  XCH3. 


HOOC.CH 


IL 


Br 

Ag2  +  ^.COOH 

/ 

(CH3)2 


,CH2 


HOOC.CH 


C.(COOH) 


CH3  (CH3)2. 
Trimethylglutaric  Acid. 


(Compare  this  reaction  with  Reaction  XL VII.) 

Reaction  XXXVIII.  (a)  Action  of  Aqueous  and  Alcoholic  Potassium  or 
Sodium  Cyanide  on  Aliphatic  Halogen  Compounds,  and  Hydrolysis  of  the 
Nitriles  so  formed.  (B.,  14,  1965 ;  15,  2318.) — The  preparation  and 
hydrolysis  of  nitriles  are  dealt  with  on  p.  146  and  p.  232  respectively. 
In  many  cases,  however,  it  is  unnecessary  to  isolate  the  nitrile  ;  it  can  be 
directly  hydrolysed  to  the  corresponding  acid  on  its  formation.  Among 
others,  the  following  syntheses  have  been  carried  out  in  this  way  : — 

(i.)  w-Valeric  acid  (pentan  acid)  from  n-butyl  bromide  (Am.  Soc,  42, 
310). 


CARBON  TO  CARBON 


119 


(ii.)  Methyl  succinic  acid  (methyl-butan  di-acid)  from  propylene  di- 
bromide. 

(iii.)  w-Pimelic  acid  (heptan  di-acid)  from  penta -methylene  di-bromide. 

(iv.)  TricarballyHc  acid  (3-carboxyl-pentan  di-acid)  from  propeny]  tri- 
bromide  (Preparation  60). 

(v.)  Citric  acid  (3-hydroxyl-3-carboxyl-pentan  di-acid)  from  di-chlor- 
acetonic  acid. 

Preparation  58. — Malonic  Acid  (Propan  di-acid). 

CH2(COOH)2.       C3H404.  104. 

100  gms.  (1  mol.)  of  powdered  chloracetic  acid  are  treated  with  150  gms. 
of  broken  ice  and  dissolved  in  125  gms.  (1  mol.)  of  33J%  caustic  soda 
solution.  If  the  liquid  is  still  acid,  it  is  exactly  neutralised  with  caustic 
soda  solution,  and  then  treated  with  a  solution  of  69  gms.  (1  mol.)  of  98% 
potassium  cyanide  in  130  gms.  of  water  which  has  been  warmed  to  40°  C. 
After  an  hour,  the  mixture  is  slowly  warmed  to  100°  and  kept  at  this 
temperature  for  1  hour.  It  is  allowed  to  cool  to  25°,  125  gms.  (1  mol.) 
of  33J%  caustic  soda  solution  are  again  added,  and  the  liquid  is 
slowly  warmed  to  100°  and  kept  at  that  temperature  until  no  more 
ammonia  is  evolved  (2 — 3  hours).  When  a  sample  of  the  liquid  treated 
with  more  sodium  hydrate  solution  gives  no  further  ammonia  on  boiling, 
the  conversion  of  the  cyanacetic  acid  into  malonic  acid  is  complete.  The 
solution  is  cooled,  acidified  with  dilute  hydrochloric  acid  and  carefully 
evaporated  to  complete  dryness  on  a  water  bath.  The  residue  is  pow- 
dered and  repeatedly  extracted  with  ether  and  the  ether  removed  on  a 
water  bath  when  malonic  acid  remains.  It  may  be  purified  by  dissolving 
in  just  sufficient  caustic  soda  solution,  boiling  with  animal  charcoal, 
acidifying,  evaporating  to  dryness,  and  extracting  with  ether  as  before. 

NaOH  NaCN 
CH2Cl.COOH  >  CH2CLCOONa  >  CH2(CN)COONa 

NaOH  HC1 
 >  CH2(COONa)2  >  CH2(COOH)2. 


Yield. — 84%  theoretical  (85  gms.).  Colourless  crystals  ;  easily  soluble 
in  water,  alcohol,  and  ether  ;  M.P.  132°  ;  loses  carbon  dioxide  yielding 
acetic  acid  at  140° — 150°.  All  malonic  acid  homologues  do  this  (see 
Reaction  XXXIII.  (b) ).    (A.,  204,  125  ;  B.,  22,  [2],  400.) 

Di- ethyl  malonate  may  be  prepared  from  chloracetic  acid  by  a  similar 
method. 

The  use  of  ice  to  keep  down  the  temperature,  and  at  the  same  time 
supply  the  amount  of  water  required  as  a  solvent  or  otherwise,  in  a  reaction 
should  be  noted. 

Preparation  59.— Succinic  Acid  (Butan  di-acid). 

COOH.CH2.CH2.COOH.       C4H604.  118. 

100  gms.  (1  mol.)  of  ethylene  dibromide  and  75  gms.  (excess)  of  potas- 
sium cyanide  in  alcoholic  solution  are  refluxed  on  a  water  bath  in  a  750-c.c. 


120  SYSTEMATIC  ORGANIC  CHEMISTRY 


round-bottomed  flask  until  potassium  bromide  ceases  to  separate  out  from 
the  solution.  The  latter  is  then  cooled  and  filtered  ;  60  gms.  (2  mols.)  of 
solid  caustic  potash  are  added,  and  the  mixture  again  remixed  on  a  water 
bath  in  a  fume  cupboard  until  the  strong  evolution  of  ammonia  gas  begins 
to  slacken.  The  flask  is  then  cooled,  and  the  contents  are  acidified  with 
dilute  hydrochloric  acid  and  carefully  evaporated  to  dryness.  The  dry 
powdered  residue  is  repeatedly  extracted  with  absolute  alcohol,  and  the 
extract  distilled  on  a  water  bath.  The  succinic  acid  remains  behind  in 
small  crystals  ;  it  is  recrystallised  from  hot  water,  decolorising  if  necessary 
with  a  little  animal  charcoal. 

CH2Br.CH2Br  +  2KCN  =  CH2(CN).CH2.CN  +  2KBr. 
(CH2CN)2  +  2KOH  +  2H20  =  (CH2COOK)2  +  2NH3. 
(CH2COOK)2  +  2HC1  =  CH2.COOH  +  2KC1 
CH2.COOH 

Yield. — 80%  theoretical  (50  gms.).  Colourless  prisms  ;  soluble  in 
water,  alcohol,  and  ether  ;  insoluble  in  chloroform  ;  sublime  above  100° 
without  decomposition ;  M.P.  180°  ;  at  235°  decompose  forming  the 
anhydride.  (P.  R.  S.,  10,  574;  A.,  120,  268.)  For  the  isolation  of 
ethylene  dicyanide,  see  p.  146.) 

Preparation  60. — Tricarballylic  Acid  (3-Carboxyl-pentan-diacid). 

CH2.COOH. 

I 

CH.COOH.        C6H806.  176. 
CH2.COOH. 

50  gms.  (1  mol.)  of  propenyl  tribromide  are  dissolved  in  excess  of 
alcohol,  36  gms.  (1  mol.)  of  coarsely  powdered  potassium  cyanide  are 
added,  and  the  whole  heated  for  15  hours  in  a  soda-water  bottle  with  the 
cork  well  tied  down  in  a  water  bath,  the  bottle  being  well  wrapped  in  a 
cloth.  A  small  autoclave  can  also  be  used.  The  bottle  is  then  cooled  in 
a  freezing  mixture,  carefully  (use  goggles)  opened,  and  the  alcoholic  liquid 
filtered  from  the  potassium  bromide  which  has  separated  out. 

The  filtrate  is  now  refluxed  on  a  water  bath  with  a  sufficient  quantity 
(40  gms.)  of  caustic  potash  to  decompose  the  cyanide  formed  until  no  more 
ammonia  is  evolved.  The  alcohol  is  distilled  off  on  a  brine  bath,  and  the 
cooled  residue  evaporated  to  dryness  with  excess  nitric  acid.  From  it, 
after  being  well  dried  and  powdered,  the  tricarballylic  acid  may  be 
extracted  with  absolute  alcohol.  The  dark-coloured  substance  obtained 
on  evaporating  of!  the  alcohol  is  recrystallised  from  hot  water  with  the 
addition  of  animal  charcoal. 

C3H5Br3  +  3KCN  =  C3H5(CN)3  +  3KBr. 
CHo(CN).CH(CN).CH2CN  +  3KOH  +  3H20  = 
CH;(COOH).CH(COOH).CH2)COOH)  +  3NH3 

Yield. — 70%  theoretical  (22  gms.).  Colourless  rhombic  plates  ;  easi y 
soluble  in  water  and  alcohol ;  M.P.  158°.    (P.  R.  S.,  14,  77.) 


CARBON  TO  CARBON 


121 


General  Methods  of  isolating  organic  acids  from  their  salts  may  here  be 
noted. 

(i.)  An  insoluble  acid  can  be  precipitated  from  a  solution  of  a  soluble 
salt  by  addition  of  dilute  hydrochloric  sulphuric  or  nitric  acids  and 
filtered  off  or  extracted  with  a  solvent  (see  Preparations  47,  52,  56, 
186,  etc.). 

(ii.)  A  volatile  acid  soluble  in  water  can  be  obtained  by  treatment  of  a 
solution  of  its  alkali  salt  with  sulphuric  acid,  dilute  or  strong,  according 
as  the  acid  is  more  or  less  volatile,  and  subsequent  distillation  (see  Pre- 
parations 53,  175). 

(iii.)  A  liquid  or  volatile  acid  soluble  in  water  may  be  isolated  by 
treatment  of  the  lead  salt  with  H2S  and  the  draining  or  evaporating  away 
of  the  acid  as  it  is  liberated  (see  Preparation  188). 

(iv.)  A  soluble  non- volatile  acid  may  be  obtained  by  evaporating  a 
soluble  salt  with  dilute  hydrochloric  or  nitric  acids  to  dryness,  and  extract- 
ing the  residue  with  a  suitable  solvent.  Hydrochloric  acid  is  usually  the 
better  to  use,  as  nitric  acid  may  oxidise  the  product  (see  Preparations  58, 
59,  60,  etc.). 

(v.)  If  the  metal  present  be  not  an  alkali  metal,  and  if  the  acid  be 
soluble,  the  former  may  be  precipitated  by  addition  of  the  exact  quantity 
of  sulphuric  acid,  say,  or  by  means  of  H2S  or  hydrochloric  acid  ;  the  filtrate 
is  then  evaporated  to  dryness  or  distilled.  Sulphuric  acid  is  used  when 
calcium,  strontium,  barium,  lead,  etc.,  are  present ;  hydrochloric  acid 
when  silver,  lead,  or  mercury  (-ous)  are  the  metals  to  be  dealt  with,  while 
H2S  is  advantageous  when  tin  or  lead  have  to  be  removed  (see  Pre- 
parations 62,  488,  etc.).  It  is  best  to  use  sulphuric  acid  where  a  subse- 
quent distillation  is  necessary. 

Reaction  XXXVIII.  (6)  Action  at  200°  of  Aqueous  or  Aqueous-alco- 
holic Potassium  Cyanide  in  presence  of  Cuprous  Cyanide  on  Aromatic 
Halogen  Compounds,  and  Hydrolysis  of  the  Nitriles  so  formed.  (B.,  52, 
[B],  1749.) — It  is  difficult  directly  to  replace  nuclear  halogen  atoms  in 
aromatic  compounds,  unless  these  atoms  be  rendered  labile  by  the  presence 
of  nitro-  or  other  negative  groups  (see  p.  194).  Lately,  however,  it  has 
been  shown  that  by  the  action  of  aqueous  or  aqueous-alcoholic  potas- 
sium cyanide  at  200°,  using  cuprous  cyanide  as  catalyst,  combined  replace- 
ment of  the  halogen  by  CN  and  hydrolysis  of  the  nitrile  so  formed  occurs. 
In  this  way  bromo-benzene  has  been  directly  converted  into  benzoic  acid, 
^)-di-bromo-benzene  into  terephthalic  acid,  and  j9-bromaniline  into  p- 
aminobenzoic  acid.  Similar  transformations  have  also  been  effected  in 
the  benzene  series  as  well  as  with  derivatives  of  naphthalene  and  thiophene. 
Copper  is  the  unique  catalyst  in  this  reaction  which  compares  in  some 
respects  with  the  older  Sandmeyer  reaction. 

Reaction  XXXVIII.  (c)  Action  of  Hydrogen  Cyanide  on  Aldehydes 
and  Ketones  and  Hydrolysis  of  the  Cyanhydrins  so  formed.  (B.,  14, 
235;  C.  Z.  (1896),  90;  C,  (1900),  I.,  402.)— As  is  explained  under 
Reaction  L  (q.v.)  aliphatic  and  aromatic  aldehydes  and  ketones  or  their 
bisulphite  compounds  react  with  hydrogen  cyanide  to  form  cyanhydrins 
(a-hydroxy -nitriles).    These  are  readily  hydrolysed  to  a-hydroxy-acids  for 


122  SYSTEMATIC  ORGANIC  CHEMISTRY 


the  preparation  of  which,  since  the  isolation  of  the  nitrile  is  unnecessary, 
the  above  reaction  is  often  directly  used. 

In  the  sugar  group  it  is  of  especial  interest,  not  only  for  its  value  in 
determining  constitution,  but  also  for  the  synthesis  of  sugar  and  other 
derivatives  containing  long  carbon  chains.  Thus  (Z-glucose  yields  in  this 
way  the  lactone  of  a-^-glucoheptonic  acid,  which  may  be  reduced  to  cn-d- 
glucoheptose — that  is  to  a  sugar  containing  one  more  secondary-alcohol 
group  than  the  original  sugar  (see  Reaction  LXV.  (b),  where  the  subject  is 
further  treated). 

In  this  way,  too,  lactic  acid  has  been  synthesised  from  acetaldehyde. 
CH3  CHO  +  HCN  ->  CH3.CH(OH)CN  — >  CH3CH(OH)COOH. 
Dichloracetonic  acid  has  been  prepared  from  dichloracetone. 

CH2C1  CH2C1 

.1  I 

CO  ->  C(OH)COOH 

<!jh2ci  CH2C1 
while  citric  acid  has  been  obtained  from  y-cyano-aceto-acetate. 

CH2CN  CH2CN  CH2COOH 

'  ' /OH  ' 

CO  C<  C(OH)COOH 

i  iXCN  _v 


CH2  CH2.COOH 


COOC2H5  COOC2H5 


Preparation  61.— Glycollic  Acid  (Ethanol  Acid). 

CH2(OH)COOH.       C2H403.  76. 

20  gms.  (1  mol.)  of  potassium  cyanide  (98%)  are  powdered  and  dissolved 
in  100  c.cs.  of  water,  26  c.cs.  (1  mol.)  of  40%  formaldehyde  are  added,  the 
mixture  warmed — not  above  30°  C. — until  homogeneous,  and  after 
standing  1  hour,  treated  slowly  in  a  good  draught  cupboard  with  cold 
dilute  hydrochloric  acid  (2  mols.  ;  64  c.cs.  cone,  acid  in  100  c.cs.  of  water), 
the  whole  being  well  stirred  during  the  addition.  Any  hydrogen  cyanide 
remaining  is  expelled  by  boiling  (caution  /)  and  the  solution  evaporated  to 
dryness  on  a  water  bath.  The  powdered  residue  is  extracted  in  a  reflux 
apparatus  with  50  c.cs.  of  boiling  acetone  and  the  filtered  extract  evaporated 
to  dryness  on  a  bath  kept  at  65°. 

H.CH  :  O  +  KCN  +  2H20  =  HCH(OH).COOK  +  NH3. 
CH2(OH).COOK  +  HC1  =  CH2(OH).COOH  +  KC1. 

Yield. — 70%  theoretical  (16  gms.).    Colourless  deliquescent  crystals  ; 


CARBON  TO  CARBON 


123 


soluble  in  water  and  in  acetone  ;  M.P.  80°  ;  K  =  152.    (B.,  14,  1965  ; 
15,  2318  ;  C.,  (1900),  L,  402.) 
Preparation  62. — oc-cZ-Glucoheptonic  Acid  (Heptan-hexol-acid). 

CH3OH.(CHOH)6.COOH.       C7H1408.  226. 

100  gms.  (1  mol.)  of  anhydrous  grape-sugar  are  dissolved  in  500  c.cs. 
(1  mol.  of  HCN)  of  3%  hydrocyanic  acid  {caution  /),  and  treated  with  10 
drops  of  ordinary  ammonia.  The  mixture  is  allowed  to  stand  for  4—5 
days  in  a  fume  cupboard  at  room  temperature,  and  is  then  treated  with  a 
solution  of  130  gms.  (excess)  of  barium  hydrate  in  400  c.cs.  of  water  and 
boiled  in  a  dish  in  a  fume  cupboard  until  the  smell  of  ammonia  has 
disappeared. 

The  liquid  is  now  acidified  with  dilute  sulphuric  acid  ;  the  hydro- 
cyanic acid  is  driven  off  by  boiling  in  a  fume  chamber  {caution  !)  and  the 
sulphuric  acid  exactly  precipitated  with  strong  baryta- water.  After 
boiling  with  animal  charcoal,  the  solution  is  filtered  and  evaporated  to  a 
syrup  on  a  water  bath.  On  long  standing,  the  lactone  of  oc-^-glucoheptonic 
acid  separates  in  crystals.  These  are  macerated  with  a  little  80%  alcohol, 
and  filtered  at  the  pump.  The  substance  is  then  dissolved  in  3  times  its 
weight  of  water,  and  treated  with  animal  charcoal  in  the  warm.  The 
filtrate  is  concentrated  and  set  aside  to  crystallise. 

CH2OH(CHOH)5CHO  ->  CH2(OH)(CHOH)5CH(OH)CN  -> 
CH2OH.(CHOH)5.CHOH.COOH. 

Yield. — 70%  theoretical  (90  gms.).  Colourless  crystals  ;  soluble  in 
water  ;  M.P.  140°.    (B.,  19,  1916  ;  23,  936  ;  A.,  270,  65,  272,  200.) 

It  is  noteworthy  that  it  is  often  preferable  to  use  the  bisulphite 
compound  of  the  aldehyde  rather  than  the  aldehyde  itself  (see  p.  151). 
The  small  quantity  of  ammonia  used  above  to  help  the  reaction  may  do 
so  by  the  momentary  formation  of  the  ammonia  compound  of  the 
aldehyde. 

|  |  /OH 

CHO  +  NH3  ->  HC< 

NH2 

I  /OH  |  .OH 

HC<  +  ->  B.C(       +  NH3. 

XNH2       HCN  \CN 

Hydrogen  cyanide  seems  to  react  in  this  way  more  readily  than  it  unites 
directly  to  the  oxy  group. 

I  l/0H 
CHO  +  HCN  ->  CH 

\  " 
\CN. 

The  lactone  of  a-^-fructose-carboxylic  acid,  M.P.  130°,  is  prepared  in 
the  same  manner  from  (^-fructose  (leevulose).  It  will  be  noted  that  from 
glucose,  four  carboxylic  acids  can  be  obtained — an  a-  and  /3-acid  from 


124  SYSTEMATIC  ORGANIC  CHEMISTRY 


each  of  the  optical  isomers  (A.,  270,  64).  Like  many  acids  containing  a 
y-hydroxy  group,  all  these  free  acids  are  unstable,  immediately  forming 
lactones  on  liberation  from  their  salts. 

Reaction  XXXIX.  Fusion  of  the  Salts  of  Aromatic  Sulphonic  Acids  with 
Sodium  Formate. — An  important  property  of  sulphonic  acids  is  the 
behaviour  of  their  salts  in  certain  fusions.  Two  of  these  are  dealt 
with  on  p.  203  and  p.  316.  The  third — fusion  with  sodium  formate  to 
obtain  carboxylic  acids — is  of  theoretical  rather  than  commercial  import- 
ance. It  is  interesting,  however,  when  considered  in  comparison  with  the 
other  two  fusions. 

C6H5.S03Na  +  H.COONa  =  C6H5.COONa  +  H.S03Na. 

The  aromatic  group  is  as  it  were  transferred  from  one  acid  radical  to 
another,  interchanging  with  hydrogen  in  so  doing. 
Reaction  XL.  Condensation  of  a  Phenol  with  a  6 '  Methane  Carbon  Atom. ' ' 

(A.,  194,  123  ;  196,  77  ;  B.,  28,  R.,  743.)— Phenols  can  be  condensed  with 
compounds  which  can  yield  a  nuclear  carbon,  to  give  dyes  of  the  rosalic 
acid  series.  The  fewco-compound — a-j93-hydroxy-triphenyl-methanol— 
first  formed,  is  unstable  and  immediately  yields  the  dyestuff,  no  oxidising 
agent  being  necessary.  In  this  respect  these  compounds  differ  from  the 
analogous  rosaniline  compounds  (see  p.  376). 

Aurin,  the  simplest  member  of  the  series,  is  prepared  by  heating  together 
phenol,  oxalic,  and  strong  sulphuric  acids  at  130°  for  6  hours. 

H2S04      y0  2C6H5OH 
(COOH)2  ->  ( +  CO)  > 


,(C6H4OH)2  r^(C6H4OH) 
C6H5OH 


[ 


V 

OH  -J 


0 

(HOC6H4)2  =  C  =  C6H4  =  0. 

The  methane  carbon  atom  can  also  be  supplied  by  formaldehyde  ;  the 
steps  in  the  synthesis  are — 

H2C  =  0  +  H-C6H4'°H        H2C(C6H4OH)2  C6H50H  +  0 


H.C6H4.OH 
r  C(C6H4OH)3-| 

|_OH  J 


(HOC6H4)2C  =  C6H4  =  0. 


Rosolic  acid  (methyl  aurin)  another  important  member  of  this  series,  is 
prepared  by  oxidising  a  mixture  of  phenol  and  o-  and  2>-cresols  with 
arsenic  acid  and  sulphuric  acid.  1  mol.  of  each  of  the  cresols  and  1  mol. 
of  phenol  react,  the  methyl  carbon  of  the  ^-cresol  molecule  serving  as 
a  nuclear  carbon. 


CARBON  TO  CARBON 


125 


CJL.OH 


HC 


H  H:C6H4.OH 

H  H:C6H3.OH 
.CH, 


30 


/C6H4OH 

/ 

HO.O— C6H4OH 

\C6H3(OH)(CH3) 


/C6H4OH 

/ 

->  C  =  C6H4  =  0 

\ 

\C.H8(OH)(CH8)[3  :  4]. 

These  compounds  dissolve  in  alkalis,  and  alcohols  with  a  bright  red 
colour,  but  they  are  now  little  used  as  dyes.  As  will  be  seen,  they  are 
assumed  to  have  a  quinonoid  formula  like  all  the  triphenylmethane  dyes 
(see  p.  374). 


\ 


CHAPTER  VII 


carbon  to  carbon 
Oxide-Oxy  Compounds 

In  this  section  those  nuclear  syntheses  of  which  the  product  is  neces- 
sarily an  ester  or  some  other  compound  containing  both  an  oxy  and  an 
oxide  (ether)  group  are  described.  Many  important  reactions  are  here 
involved — partly  owing  to  the  activating  influence  of  the  oxy-group,  and 
partly  because  the  inertness  of  the  oxide-group  enables  oxy  compounds 
containing  it  to  be  used,  where  the  corresponding  hydroxy-oxy  compound 
(acid)  is  inadmissible,  owing  to  the  reactivity  of  its  hydroxyl  group.  On 
this  account,  these  ester  syntheses  are  very  often  only  undertaken  to 
obtain  an  acid  by  an  after-hydrolysis. 

Reaction  XLI.  Elimination  of  Water  from  o-Phenoxy-benzoic  Acids 
(o-Phenyl-salicylic  acids).  (B.,  21,  502;  25,  1652;  26,  71.)— The 
xanthones  (di-benzpyrones)  possess  a  chromogenic  nature,  and  form  the 
basis  of  some  dyestuffs.  They  are  obtained  by  loss  of  water  from  the 
o-phenoxy -benzoic  acids  by  treating  the  latter  with  dehydrating  agents- 
cone,  sulphuric  acid  at  100°,  fused  zinc  chloride,  or  acetic  anhydride. 


/0\ 


0 


11 


OH 


\/\CO 
o-Phenoxy -benzoic  acid. 


0 

Xanthone. 


They  have  also  been  synthesised  by  condensing  salicylic  acid  with 
phenols  through  the  agency  of  sulphuric  acid,  acetic  anhydride,  etc.  (B., 
21,  502  ;  24,  3982  ;  25,  1652  ;  26,  71  ;  27,  1989  ;  A.,  254,  265.)  All  four 
possible  mono-hydroxy  xanthones  have  been  prepared  in  this  way,  as 
have  some  of  the  poly-hydroxy  compounds.  These  latter  are  the  more 
important. 


(HO)C6H: 


H 


OH 


OH. CO, 


+ 


oh/ 


C6H4 


HOCfiH, 


,CQ 


0 


The  xanthones  are  allied  to  the  thio-xanthones  (J.  C.  S.,  97,  1290)  the 
acridones  (B.,  25,  1734)  and  the  fluorones  (J.  C.  S.,  99,  545).    The  mother 

126 


CARBON  TO  CARBON 


127 


substance  obtained  by  reduction  of  xanthone  is  xanthene  (methylene-di- 
phenylene  oxide).  (B.,  26,  72.) 


0 

Xanthene.  Fluorone. 


Although  the  xanthones  contain  a  ketone  oxygen  atom,  they,  like  the 
pyrones  (see  p.  378),  do  not  react  with  hydroxylamine,  or  phenyl 
hydrazine. 

Reaction  XLIL  Prolonged  action  of  Heat  on  Ethyl  Aceto-acetate.  (A., 
273,  186.) — By  prolonged  boiling  of  aceto-acetic  ester  under  a  reflux  con- 
denser at  ordinary  pressures,  condensation  occurs,  and  dehydracetic  acid 
is  formed.  The  parent  acid,  a  8-hydroxy-acid,  is  unstable,  and  has  not 
yet  been  isolated. 

CO.OEt.     HO.C.CH3  CO — 0 — C.CH3 

I  [I        ->         I  II       +  2EtOH. 

CH3.CO.CH2     EtO.CO.CH     CH3.CO.CH— CO— CH 

1  mol.  of  the  keto-  reacts  with  1  mol.  of  the  enol-form  ;  it  will  be  noted 
how  the  activated  methylene  group  enters  into  the  reaction. 

The  lactone  formed  is  important,  because  hydriodic  acid  reduces  it  to 

1     0  [ 

di-methyl  pyrone  CH3C :  CH.CO.CH :  C.CH3,  a  certain  amount  of  re- 
arrangement occurring.  This  latter  compound  is,  like  all  the  pyrones,  of 
great  theoretical  interest  (see  p.  378).  Also  dehydracetic  acid  figures 
in  the  chemistry  of  the  ketenes,  ketene  itself  polymerising  to  it,  under  the 
influence  of  zinc  bromide  or  tertiary  amines,  or  even  spontaneously. 

CO    0  =  C  :  CH2     (C2H5)3N  CO — 0 — C.CH3 

II   >  I  II 

CH2=CO  CH2  0  :  C  =  CH2  CH3.CO.CH— CO— CH. 

(A.,  273,  186  ;  C,  1900,  II.,  625  ;  A,  257,  261.) 
Preparation  63. — Dehydracetic  Acid  (Methyl-aceto-pyronon)  (Feist). 

CO  — 0  — C.CH3. 

I  ||  C8H804.  168. 

CH3.CO.CH — CO — CH 

20  gms.  (2  mols.)  of  ethyl  aceto-acetate  are  boiled  under  a  reflux  for  6 
hours,  pieces  of  porous  porcelain  being  added  to  promote  regular  ebullition. 
The  liquid  is  then  distilled  to  200°  ;  the  distillate  may  be  fractionated  in 
vacuo  to  recover  unchanged  aceto-acetic  ester  (see  Preparation  73).  The 
brown  residue  solidifies  on  cooling  to  a  crystalline  mass.  It  is  boiled  with 
5N  caustic  soda  solution  with  the  addition  of  animal  charcoal  and  filtered 


128  SYSTEMATIC  ORGANIC  CHEMISTRY 


hot.  The  sodium  salt  crystallises  from  the  nitrate  ;  acidification  with 
dilute  sulphuric  acid  precipitates  the  required  lactone. 

2CH3.CO.CH2COOC2H5  =  C8H804  +  2C2H5OH. 

Yield. — 80%  theoretical,  allowing  for  aceto-acetic  ester  recovered  (5  gms. 
on  each  10  gms.  of  aceto-acetic  ester  used).  Colourless  needles  ;  insoluble 
in  water  ;  M.P.  108°  ;  B.P.  760  2  69° ;  K  =  0-00053.  (A.,  257,  261  ; 
B.,  27,  R.,  417.) 

Reaction  XLIII.  (a)  Formation  of  Esters  by  the  action  of  Acid  Anhy- 
drides or  of  Acid  Chlorides  on  an  Alcohol  in  the  presence  of  Magnesium 
Alkyl  Halide  (Grignard).  (B.,  39, 1738.)— This  application  of  the  Grignard 
reaction  to  the  preparation  of  esters  is  of  theoretical  rather  than  practical 
interest  as  illustrating  the  wide  applicability  of  this  many-sided  reaction. 
The  steps  in  the  synthesis  will  be  clear  from  the  examples  given  ;  they  are 
somewhat  different  from  the  usual  phases  of  a  Grignard  reaction. 

(i.)  RMgl  +  (CH3)3C(OH)  =  (CH3)3COMgI  +  E.H. 
2(CH3)3COMgI  +  (CH3CO)20  -> 
/OMgl 

CH3.C-O.C(CH3)3 

\0   >  2CH3.CO.O.C.(CH3)3  +  (IMg)aO. 

CH3.C~OC(CH3)3 
^OMgl 

(ii.)  (CH3)3COMgI  +  CH3COCl  =  CH3CO.O.C(CH3)3  +  MgClI. 

Iso-amyl  acetate  has  been  obtained  in  this  way  from  isoamyl  alcohol 
and  acetyl  chloride.  The  method  does  not  offer  any  advantages  over  the 
more  usual  esterification  reactions. 

For  the  general  experimental  method  and  precautions  necessary  in 
Grignard  reactions,  see  Preparation  18. 

Reaction  XLIII.  (b)  Formation  of  Ethyl  Esters  by  the  action  of  Ethyl 
Chloroformate  on  Magnesium  Alkyl  Halide  in  Dry  Ethereal  Solution  (Grig- 
nard).— This  is  another  mode  of  application  of  the  Grignard  reaction  to 
the  synthesis  of  esters.    It  is  more  direct  than  the  previous  method. 

/OMgCl 

CH3Mg.Cl  +  Cl.COOC2H5  ->•  Cl.C.OC2H5  ->  CH3.COOC2H5  +  MgCl2. 

\CH3 

Reaction  XLIII.  (c)  Condensation  of  a-Halogen  Fatty  Acid  Esters  with 
Aldehydes  and  Ketones  by  means  of  Zinc  or  Magnesium  (Reformatsky- 
Grignard).  (C,  (1901),  I.,  1196  ;  IL,30;  (1902),  I.,  856.)— This  is  an  exten- 
sion of  the  Grignard  and  zinc  alkyl  reactions  which  enables  a-halogen  esters 
to  be  condensed  with  oxy  compounds  as  if  they  were  simple  alkyl  halogen 
compounds.  The  zinc  or  magnesium  alkyl  derivative  is  neither  prepared 
beforehand  nor  isolated  in  the  reaction,  but  there  is  little  doubt  that  some 
such  compound  is  transitorily  formed.    Zinc  is  the  metal  most  usually 


CARBON  TO  CARBON 


129 


employed.  The  product  is  a  /3-hydroxy  ester,  and  the  method  is  the 
standard  one  for  obtaining  the  higher  ^-hydroxy  acids.  The  equation 
below  will  illustrate  this  : — 

ZnBr 

CH3.CHBr.COOC2H5  +  Zn  ->  CH3CH(COOC2H5). 
ZnBr 

CH3.CHO  +  CH3.iH(COOC2H6)  -> 
OZnBr 

I  H20 

CH3.CH(CHCH3).COOC2H5  > 

OH 

I 

CH3CH(CH.CH3).COOC2H5 

Preparation  64. — Ethyl  /^hy<koxy-a/3-dimethylbutyrate  (ethyl  ester  of 
2.3-dimethyl-3-butanol  acid). 

™3\C(0H).CH(CH3).C00C2H5.       C8H1603.  160. 

60  gms.  of  zinc  are  freed  from  oxide  and  oil  by  washing  successively  with 
warm  caustic  soda  solution,  then  dilute  acid,  water  and  alcohol.  After 
being  dried  in  an  air  oven,  a  small  quantity  is  added  to  a  mixture  of  90  gms. 
pure  dry  acetone  and  182  gms.  of  ethyl  a-bromopropionate  contained  in  a 
large  flask  provided  with  a  reflux  condenser.  The  flask  is  gradually 
warmed  on  a  water  bath  until  a  reaction  commences,  and  if  it  proceeds  too 
vigorously,  cooling  must  be  applied.  More  zinc  is  added  from  time  to 
time  as  the  action  subsides,  until  some  of  the  metal  remains  undissolved 
(about  45  gms.  Zn  are  usually  required),  and  after  the  final  addition,  heat- 
ing is  continued  for  2 — 3  hours.  The  syrupy  liquid  is  poured  off  from  the 
unattacked  metal,  and  water  added.  The  basic  zinc  bromide  which  is 
precipitated  is  dissolved  by  the  addition  of  a  sufficient  quantity  of  dilute 
sulphuric  acid,  and  the  oily  layer  is  extracted  with  ether  and  separated. 
The  extract  is  washed  three  times  with  dilute  sulphuric  acid,  then  with 
water,  and  dried  over  calcium  chloride.  After  the  ether  is  removed,  the 
residue  is  distilled  at  30  mms.  pressure,  when  the  pure  ester  passes  over 
about  105°. 


CH3CHBrCOOC2H5  +  Zn  ->  BrZn-  CH(CH3)COOC2H5. 

CH3 

I  CH3 
CO  +  BrZnCH(CH3)COOC2H5->  I  /OZnBr 

C\ 

CH3  I  \CHCH3.COOC2H5 

CH3 

H90 


2' 
 > 


CH3C(OH)CH3CH(CH3)COOC2H5. 


Zn(CH(CH3)COOC2H5)2  might  also  be  considered  an  intermediate  com- 
pound in  the  reaction. 

s.o.c.  K 


130 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Yield. — 50%  theoretical  (60  gms.).  Colourless  oil,  insoluble  in  water  ; 
B.P.  30,  105°.    (C,  (1901),  L,  1196  ;  II.,  30  ;  (1902),  L,  856.) 

Reaction  XLIII.  (d)  Condensation  o£  Di-ethyl  Oxalate  with  Alkyl 
Halides  in  the  presence  of  Zinc  (Frankland — Duppa).  (A.,  185,  184.) — 
This  is  a  type  of  condensation  very  similar  to  those  just  described.  The 
zinc  alkyl  is  not  isolated,  and  simple  halogen  compounds  are  used.  The 
product  is  a  derivative  of  glycollic  acid. 

^/OC2H5      Zn  ^/OCaHs 
2CH3I  +  C  =  O  ->  C  -  CH3 

\C00C2H5  I  \0ZnCH3     Ln  + 

COOC2H5 

/CH3  /CH3 

C— CH3  H20     C  —  CH3 

|  \0ZnCH3  >    |  \OH 

COOC2H5  COOC2H5. 

Reaction  XLIV.  (a)  Condensation  oi  Alkyl  and  Aryl  Halides  with  Ethyl 
Sodio-malonate  and  its  Homologues.  (B.,  7, 1383 ;  Am.  Soc.  (1921),  680.)— 
The  malonic  esters  are  almost  as  valuable  as  the  aceto-acetic  esters  (see 
Reaction  XLIV.  (b)  )  in  the  synthesis  of  mono-  and  poly-carboxylic  acids 
owing  to  the  successive  replaceability  by  sodium  of  the  hydrogen  atoms 
of  the  methylene  group,  activated  as  it  is  by  two  neighbouring  carbonyl 
groups.  These  sodio  derivatives  are  very  reactive,  and  undergo  the 
following  changes  : — 

(i.)  By  the  action  of  alkyl  halide  on  the  sodio  compound,  a  mono-alkyl 
compound  is  formed. 

Na  RI 
CH2(COOC2H5)2  ->  CHNa(COOC2H5)2  ->  CHR(COOC2H5)2. 

(ii.)  By  the  action  of  alkyl  halide  on  the  sodio  derivative  of  a  mono- 
alkyl  malonic  ester,  a  di-alkyl  compound  is  produced. 

Na  RJ 
CHR(COOC2H5)2  ->  CNaR(COOC2H5)2  ->  CR1R(COOC2H5)2. 

From  these  esters  the  corresponding  dibasic  acids  can  be  obtained  by 
hydrolysis,  so  that  the  homologues  of  malonic  acid  can  be  synthesised  in 
this  way. 

Again,  as  all  these  acids  have  two  carboxyls  attached  to  the  same 
carbon  atom,  they  lose  carbon  dioxide  on  heating  and  pass  into  mono- 
basic fatty  acids  (B.,  27,  1177).  This  affords  an  important  and  standard 
synthesis  for  these  latter  acids  (see  Preparation  426,  also  Preparations  58 
and  p.  107). 

(iii.)  Cyclo  paraffin  derivatives  can  also  be  synthesised.  Malonic  ester 
and  ethylene  bromide  in  the  presence  of  sodium  alcoholate  yield  tri- 
methylene-di-carboxylic  ester  and  thence  a  di-  and  mono-carboxyhc  acid. 
(Am.  Soc,  42,  314  ;  43,  680.) 


CARBON  TO  CARBON 


131 


CH2Br  CH2(COOC2H5), 

I  + 
CELBr 


C2H5ONa 


CH, 


CH9 


>  CH— CH(COOC2II5)2. 
CH2Br 

(This  compound  can  be  isolated  by  using 
an  excess  of  the  alkylene  bromide). 

CH2 


C(COOC2H6)a 


;C(COOH)< 


CH. 


— >  |^CHCOOH. 
CH2 

C2H5ONa  is  more  frequently  used  to  obtain  the  sodio  derivatives  of  the 
malonic  esters,  though  metallic  sodium  can  also  be  employed. 

By  using  various  alkylene  dibromides,  4,  5,  6  or  7,  membered  rings  can 
also  be  obtained.    (A.,  284,  197.) 

(iv.)  Simultaneously  there  is  formed  in  the  above  reaction  butane-tetra- 
carboxylic  ester,  and  it  yields  a  tetra-  and  thence  a  dibasic  acid  (adipic 
acid).  The  tetra-basic  ester  can  also  yield  ring  compounds  (Reaction 
XLVIL). 

CH2Br  CH2CH(COOC2H5)2 

I  +  2CHNa(COOC2H5)2   >  j 

CH2Br  CH2CH(COOC2H5)2 
CH2CH(COOH)2     (heat)  CH2CH2COOH 

~>  I   >  I 

CH2CH(COOH)2  CH2CH2COOH. 

(v.)  Also  by  starting  with  compounds  such  as  I.,  ring  compounds  may 
be  synthesised  by  intra-molecular  condensation. 


CH(COOC2H5)2 


C2H5ONa 


CNa(COOC2H5)2 


 CBr 

/\ 
I 


R 


-CBr 


Ri 


C(COOC2H5)2 

R  — 1 
Rn 

(vi.)  Halogen  esters  react  like  simple  alkyl  halides. 


CH2C1C00C2H5  +  CH2(COOC2H5)2 
CH(COOC2H5)2 

I 

CH2(COOC2H5) 
Ethane -tricarboxylic  Ester. 


CH.ONa 


132  SYSTEMATIC  ORGANIC  CHEMISTRY 


(vii.)  The  acyl  malonic  esters  are  produced  from  the  acyl  chlorides,  and 
sodio-malonic  ester  in  a  manner  exactly  analogous  to  the  alkyl  malonic 
esters  (B.,  20,  R.,  381). 

Benzoyl  chloride,  and  sodio  ethyl  malonate  yield  benzoyl-malonic  ester. 

C6H5C0C1  +  CHNa(COOC2H5)2->  (C6H5CO)CH(COOC2H5)2. 

The  structure  of  the  sodio  derivatives  of  diketomethylene  compounds 
like  malonic  ester,  is  dealt  with  in  Reaction  XLIV.  (b),  and  an  explanation 
is  given  as  to  why  only  one  hydrogen  is  replaceable  at  a  time. 

Pkepaeation  65. — Ethyl-malonic  Ester. 

C2H5CH(COOC2H5)2.       C9H1604.  188. 

To  25  gms.  of  absolute  alcohol  contained  in  a  flask  provided  with  a 
reflux  condenser,  2-3  gms.  of  sodium  are  added,  and  when  the  metal  has 
dissolved,  16  gms.  of  ethyl  malonate  are  added.  The  sodio-derivative  of 
the  ester  is  precipitated  as  a  white  solid.  The  flask  is  shaken  while  20  gms. 
of  ethyl  iodide  are  slowly  run  in  from  a  dropping  funnel ;  the  precipitate 
gradually  reacts  and  sodium  iodide  is  deposited.  Heating  is  conducted 
on  a  water  bath  (1 — 2  hours)  until  the  product  ceases  to  show  an  alkaline 
reaction.  The  alcohol  is  distilled  off,  the  residue  diluted  with  water  and 
extracted  with  ether.  The  extract  is  dried  over  calcium  chloride,  the 
ether  distilled  off,  and  the  residue  fractionated,  when  the  product  passes 
over  at  200°— 210°. 

CH2(COOC2H5)2  ->  CHNa(COOC2H5)2  ->  C2H5.CH(COOC2H5)2. 

Yield. — 75%  theoretical  (15  gms.).  Colourless  oil  of  fruity  odour  ; 
B.P.  207°  ;  D.  l*  1-008.    (A.,  204,  134.) 

Methyl,  propyl,  butyl,  etc.,  malonic  esters  are  also  obtained  in  a  similar 
manner.  It  is  to  be  observed  that  aryl  halides  do  not  undergo  this  re- 
action. The  di-alkyl  esters  are  obtained  from  the  mono-alkyl  esters  in 
the  same  way  as  the  latter  are  obtained  from  malonic  ester.  But  although 
di-alkyl  compounds  are  not  formed  directly  in  any  quantity,  yet  it 
frequently  happens  that  a  little  is  obtained  in  the  preparation  of  the 
mono-alkyl  compound  from  1  mol.  of  sodium  ethoxide  and  1  mol.  of 
alkyl  halide,  owing  to  the  product  sought  for  reacting  with  more  sodium 
and  alkyl  halide.  This  may  be  prevented  when  necessary  by  using  only 
half  the  calculated  quantity  of  sodium  and  alkyl  halide.  By  this  means 
the  yield  of  benzoyl  malonic  ester  for  example  is  raised  from  55%  to  85% 
in  its  preparation  from  sodium,  benzoyl  chloride  and  malonic  ester.  (B., 
44,  1507.) 

Reaction  XLIV.  (6)  Condensation  of  Alkyl  and  Aryl  Halogen  Com- 
pounds with  the  Sodio-  and  other  Metallo-  derivatives  of  Aceto-acetic 
Ester  and  its  Homologues.    (A.,  186,  214 ;  201,  143 ;  213,  143.)— Like 

malonic  ester,  aceto-acetic  ester  contains  two  1  :  3-carbonyl  groups  with 
a  methylene  group  in  position  2.  It  is  only  to  be  expected  then  that  it 
yields  with  metallic  sodium  or  sodium  alcoholate  sodio  derivatives  from 
which  mono-  and  di-,  alkyl  and  aryl  homologues  can  be  obtained  by  treat- 
ment with  a  suitable  halide,  including  halogen  esters.  Aceto-acetic  acid 
shows  the  same  property,  but  its  great  instability  necessitates  the  use  of 


CARBON  TO  CARBON 


133 


its  very  stable  ethyl  ester.  Other  examples  of  1  :  3  di-keto-2-methylene 
compounds,  of  which  all  possess  similar  properties  to  the  esters  described 
in  this  and  the  previous  reaction  will  be  found  on  p.  91.  Reference  may 
also  be  made  to  Reaction  XLVI. 

These  compounds  are  alike  in  being  tautomeric,  the  keto  and  enol  forms 
being  in  an  equilibrium  which  varies  both  with  substance  and  with 
temperature— 

— CO.CH2.CO  —  ~  >  —  C(OH) :  CH.CO— 

and 

— CO.CHE.CO  —  >  —  C(OH) :  CR.CO— 

It  is  this  equilibrium  which  renders  difficult  the  explanation  of  the  course 
of  the  reactions  which  take  place  when  metallic  sodium  or  sodium  ethoxide 
and  then  alkyl  or  acyl  halide  are  added  to  these  compounds.  At  first 
it  was  thought  that  the  sodio-compound  formed  with  acetoacetic  ester 
was  CH3.CO.CHNa.COOC2H5,  because  the  reaction  with  alkyl  and 
acyl  halides  always  yielded  a  C-derivative,  CH3.CO.CHR.COOC2H5.  The 
first  example  of  a  different  course  of  reaction  was  found  in  the  formation 
of  an  O-derivative — j8-carbethoxy-hydroxy-crotonic  ester  from  sodio- 
aceto-acetic  ester  and  chloroformic  ester  (J.  pr.,  [2],  37,  473  ;  B.,  25,  1760  ; 
A.,  277,  64).  This  could  only  be  explained  by  assigning  an  enol  formula 
to  the  sodium  salt — 

CH3C(ONa) :  CHCOOC2H5  +  C1C00C2H5-^ 
CH3.C(OCOOC2H5)  :  CHCOOC2H5. 

This  immediately  explained  why  only  one  of  the  methylene  hydrogen 
atoms  is  replaceable  at  a  time.  The  formation  of  C-derivatives  could  then 
be  looked  on  as  an  addition  reaction  followed  by  the  separation  of  sodium 
halide. 

A 

I  CH3  C(ONa) 

II         +  i  — >         I  -> 
CH  CH3  CH 

I       .  Nil 


COOC2H5  COOC2H, 
CH.CO 


CH(CH3)        +  Nal. 

I 

COOC2H5 

Some  of  the  C-derivative,  acetyl-malonic  ester,  is  also  formed  in  the 
chloroformic  ester  condensation  quoted  above.  In  the  majority  of  cases 
the  C-derivative  is  produced  to  the  exclusion  of  the  O-derivative.  For  an 
explanation,  see  J.  pr.,  [2],  37,  473  ;  see  also  equation  (4),  p.  134. 

The  various  alkyl  derivatives  of  aceto-acetic  ester  are  important,  because 
of  the  hydrolyses  they  undergo  (see  p.  182).  Some  reference  to  the 
structure  of  the  acetoacetic  ester  will  be  found  under  Reaction  XLVI., 
p.  140  ;  the  reactions  which  it  undergoes  are  discussed  in  Reactions 
XLVIL,  Lin. 


134  SYSTEMATIC  ORGANIC  CHEMISTRY 

The  following  equations  will  illustrate  some  extensions  of  which  the 
reaction  is  capable  : — • 

(1)  C6H5.CC12.C6H5    +    CH3C  :  CH.COOC2H5     (Cu'  =  ^ 

6 

Benzophenone  Dichloride.  Cu' 

Cuproaceto- acetic  Ester. 

CH3COCHCOOC2H5 

/ 

(C,H5)aC— CI 

->        CH3C  :  CCOOC2H5  CH3CO.CCOOC2H5 

/     I  ">  II 
Cu'O      C(C6H5)2  C(C6H5)2 

/  Diphenyl-aceto- aery  Hie 

CI  Ester. 

The  reaction  may  be  assumed  to  go  as  above.  The  copper  derivative 
of  aceto-acetic  ester  is  formed  by  adding  a  saturated  alcoholic  solu- 
tion of  cupric  acetate  to  the  ester  ;  a  bluish-green  crystalline  precipitate 
(C6H903)2  Cu  is  produced  (cf.  p.  92). 

rixr 

\  >C  :  CHCOOC2H6 
/C1  /O/ 

(2)  CO       +  Cu 

\C  :  CHCOOC2H5 
Carbonyl  Chloride  CH3 

CH3COCH.COOC9H5 

/ 
CO 

CH3COCH.COOC2H5. 
Carbonyl  Diaceto -acetic  Ester. 

The  latter  compound  is  important  in  the  synthesis  of  y-pyrone. 

(3)  Attention  may  also  be  drawn  to  the  synthesis  of  ethyl  di-keto- 
camphorate  from  ethyl  di-ketocamphopyrate  (see  Reaction  XL VI.  (in.)  ). 

OC  CH  —  COOC2H5 

X>»CH3)2 


OC  CH 
OC  CH  COOC2H5 


>C(CH3) 


OC  C  COOC2H5 

I 

CH3 

(4)  It  is  of  interest  to  note  that  while  chloroformic  ester  yields  mostly 


CARBON  TO  CARBON 


J  35 


the  O-derivative,  it  is  only  the  C-derivative  that  is  obtained  from  chloro- 
acetic  ester. 

CH2Cl.COOC2H5  +  CH3C(ONa) :  CHCOOC2H5 
-*  CH3COCH(CH2C06CaH5)COOC2H8. 

Acetyl-succinic  Ester. 

On  the  other  hand,  chloroformic  ester  yields  the  C-derivative  with 
cuproaceto-acetic  ester.    (B.,  37,  3394,  4627  ;  38,  22.) 

(5)  In  the  previous  reaction  (v.),  ring  compounds  may  be  synthesised 
by  intramolecular  condensation. 

COCH2COOC2H5  COCHNaCOOC2H5 
C2H5ONa 

R  CBr  R  CBr 


t  \  /  \ 

Rj   R2  Rj  Rc 


CO —    — CHCOOC2H5 


c 

Pw 


R 


The  following  preparations  show  the  experimental  methods  used.  It 
is  to  be  noted  that  in  all  these  reactions  bromides  and  iodides  give  better 
yields  than  chlorides. 

Pkepakation  66. — Ethyl-aceto-acetic  Ester  (Ethyl  ester  of  2-ethyl-3-on- 
butan  acid). 

CH3.CO.CH(C2H5)COOC2H5.       C8H1403.  158. 

32-5  gms.  (1  mol.)  of  aceto-acetic  ester  are  slowly  added  with  cooling  to 
the  solution  obtained  by  dissolving  5-7  gms.  (1  atom)  of  clean  sodium  wire 
in  70  gms.  of  absolute  alcohol  under  a  reflux.  40  gms.  (1  mol.)  of  ethyl 
iodide  are  then  slowly  added,  and  the  whole  refluxed  on  a  water  bath 
until  it  shows  a  neutral  reaction.  If  necessary  a  little  more  ethyl  iodide  is 
added.  The  alcohol  is  removed  on  a  water  bath  and  the  residual  oil 
shaken  with  water  and  extracted  with  ether.  The  ethereal  extract  is 
dried  over  anhydrous  potassium  carbonate,  the  ether  removed  on  a  water 
bath,  and  the  residue  distilled,  the  portion  boiling  at  190° — 198°  at  760  mms. 
being  collected  separately.  If  preferred,  the  fractionation  can  be  done 
under  reduced  pressure. 

C2H5ONa  C2H5I 

CH3.CO.CH2.COOEt  >  CH3.CO.CHNa.COOEt  > 

CH3.CO.CH(C2H5)COOEt. 

Yield. — 80%  theoretical  (32  gms.).  Colourless  oil  ;  insoluble  in  water  ; 
B.P.  14  84° ;  B.P.  760  198° ;  D.  ?  0-9834.  (A.,  186,  220  ;  192,  153 ;  C, 
(1904),  II.,  309.) 

Other  mono-alkyl  aceto-acetic  esters  may  be  prepared  in  an  exactly 
analogous  manner,  using  corresponding  molecular  quantities  of  the  alkyl 
iodides. 


136  SYSTEMATIC  ORGANIC  CHEMISTRY 


In  the  preparation  of  some  of  the  higher  mono-alkyl  aceto-acetic  esters 
the  yield  is  sensibly  lowered,  owing  to  the  formation  of  di-alkyl  compounds 
due  to  secondary  reactions  of  the  same  type  as  those  described  on  p.  132. 
This  in  like  manner  can  be  remedied  by  using  only  half  the  calculated 
quantity  of  sodium  and  alkyl  halide.  The  unattacked  aceto-acetic  ester 
is  recovered  by  distillation. 

Preparation  67. — Benzyl  Aceto-Acetic  Ester. 

CH3COCH(CH2C6H5)COOC2H5.       C13H1603.  220. 

To  a  solution  of  6  gms.  (1  atom)  of  sodium  in  75  c.cs.  (excess)  of  absolute 
alcohol  are  gradually  added  65  gms.  (2  mols.)  of  aceto-acetic  ester.  32  gms. 
benzyl  chloride  are  dropped  in,  and  the  temperature  of  the  mixture  is 
maintained  at  30°  for  an  hour.  It  is  then  refluxed  for  an  hour.  The 
product  is  distilled  under  reduced  pressure,  the  fraction  164° — 165°  at 

14  mms.  consisting  of  benzyl  aceto-acetic  ester  being  retained.  Up  to 
this  temperature,  the  unattacked  aceto-acetic  ester  passes  over. 

CH3COCHNaCOOC2H5  +  C6H5CH2C1  CH3COCH(CH2C6H5)COOC2H5. 

Yield.— 85%  theoretical  (47  gms.).  Colourless  oil ;  B.P.  14  165°  ; 
B.P. 760  2  76°  ;  insoluble  in  water.    (A.,  204,  179.) 

An  equally  good  yield  can  be  obtained  by  replacing  the  ethyl  alcohol  by 
100  c.cs.  butyl  alcohol. 

The  di-alkyl  esters  are  made  from  the  mono-alkyl  esters  in  a  manner 
exactly  similar  to  that  by  which  the  mono-alkyl  esters  are  made  from 
aceto-acetic  ester  itself. 

The  method  of  preparation  of  acyl  aceto-acetic  esters  is  exemplified  in 
the  following.  The  reaction  goes  through  phases  similar  to  those  described 
for  alkyl  compounds,  but  owing  to  the  greater  reactivity  of  the  acyl 
halides,  special  precautions  have  to  be  taken.  Unlike  the  alkyl  chlorides, 
the  acyl  chlorides  give  good  yields  ;  there  is  no  need  to  use  the  bromides 
or  the  iodides. 

Preparation  68. — Benzoyl  Aceto-Acetic  Ester. 

COC6H5 

I 

CH3COCH.COOC2H5.       C13H1404.  234. 

To  600  c.cs.  of  absolute  alcohol  in  a  flask  attached  to  a  reflux  are  gradually 
added  35  gms.  (2  atoms)  of  sodium  cut  in  small  pieces.  When  all  the 
sodium  has  dissolved,  the  solution  is  cooled.  To  300  c.cs.  of  this  solution 
are  added  100  gms.  (1  mol.)  of  aceto-acetic  ester,  and  with  continual 
stirring,  45  c.cs.  of  benzoyl  chloride  are  dropped  in  from  a  burette  during 

15  minutes,  the  temperature  being  kept  below  10°.  After  30  minutes, 
150  c.cs.  of  the  original  solution  and  22  c.cs.  benzoyl  chloride  are  added  as 
before.  This  process  is  repeated  until  all  the  original  solution  is  used  up, 
and  90  c.cs.  benzoyl  chloride  in  all.  After  12  hours,  the  sodium  salt  is 
filtered  off  and  washed  with  ether.  By  acidifying  with  dilute  acetic  acid 
in  the  presence  of  ice-water,  the  ester  is  liberated,  extracted  with  ether, 
dried  over  anhydrous  sodium  sulphate,  and  the  ether  removed.  The 


CARBON  TO  CARBON 


137 


residue  is  then  distilled  under  reduced  pressure,  the  fraction  173°— 177° 
at  12  mms.  being  retained. 

CH3CO.CHNaCOOC2H5  +  C6H5C0C1 ->  CH3COCH(COC6H5)COOC2H5. 

Viscous  oil ;  insoluble  in  water  ;  B.P.  12 ,  175°,  with  slight  decomposi- 
tion ;  tautomeric.    (B.,  18,  2131  ;  44,  1507.) 

Reaction  XLIV.  (c)  Condensation  of  Alkyl  and  Acyl  Halides  with 
the  Sodio-derivatives  of  Cyanacetic  Ester.    (B.,  20,  R.,  477  ;  21,  R.,  353  ; 

27,  R.,  262  ;  C,  (1900),  II,  38  ;  (1905),  I,  150  ;  J.  pr,  [2]  51,  186.)— 
Cyanacetic  ester,  CH2(CN)COOC2H5  has  similar  properties  to  malonic 
and  aceto-acetic  esters,  inasmuch  as  the  methylene  hydrogen  atoms  are 
successively  replacable  by  sodium  and  this  latter  by  alkyl  and  acyl 
radicals. 

C  :  N       Na  C  j  N  C  j  N 

or  | 
C2H5ONa  EI 

 >        I   > 

CH2  CH  CHE 

|/°Na 

COOC2H5  \QCtfI. 

The  activation  of  the  methylene  hydrogens  is  connected  not  only  with 
the  presence  of  oxy  groups,  but  also  is  influenced  by  other  groups  con- 
taining double  and  multiple  linkings.  This  is  somewhat  analogous  to  the 
activating  effect  of  nitro  groups  in  aromatic  compounds.  Reference  may 
also  be  made  to  the  hydroxymethylene  compounds,  Reaction  XXIII.  (a). 

The  groups  C  :  O  and  C  \  N  resemble  one  another  in  many  of  their 
reactions.  It  may  be  noted  that  unsaturated  groups  always  tend  to  give 
an  acid  character  to  any  compound  in  which  they  occur. 

The  synthesis,  like  its  analogues,  may  be  extended  to  halogen  esters. 

C2H5ONa  CH2COOC2H5. 

CH2ICOOC2H5  +  CN.CH2COOC2H5  >  CN.CH(COOC2H5) 

Cyano -succinic  Ester. 

Reaction  XLV.  Condensation  of  Aldehydes  and  Ketones  with  certain 
Esters  under  the  influence  of  Acetic  Anhydride,  Hydrochloric  Acid,  Sodium 
Ethoxide  or  certain  bases.  (A.,  218,  172  ;  B.,  29,  172  ;  30,  481  ;  31,  735, 
2585.) — 1  mol.  of  an  aldehyde  can  be  made  to  condense  with  1  mol.  of  an 
ester  containing  an  a-methylene  group,  thus 

KiCHO  +  RCH2COOC2H5  -  EXCH  :  CRCOOC2H5. 

If  hydrochloric  acid  or  acetic  anhydride  be  used,  both  aliphatic  and 
aromatic  aldehydes  can  be  employed,  but  if  sodium  ethoxide  or  small 
quantities  of  diethylamine,  piperidene,  quinoline,  etc.,  be  taken,  aromatic 
aldehydes  also  will  react.  In  these  reactions  the  methyl  gives  better 
results  than  the  ethyl  ester. 


138  SYSTEMATIC  ORGANIC  CHEMISTRY 


Esters,  such  as  those  of  malonic,  aceto-acetic  or  cyanacetic  acids,  in 
which  the  methylene  group  is  doubly  activated,  will  condense  even  with 
ketones.  By  varying  the  proportion  of  aldehyde  or  ketone  to  ester,  2 
mols.  of  the  former  can  be  made  to  condense  with  1  of  the  latter,  using 
the  basic  condensing  agents  only  (4,  below).  The  following  will  illustrate 
these  points  : — 

HClor  (CHoCOUO 

(1)  C6H5.CHO  +  CH2(COOC2H5)2  -   > 

C6H5CH  :  C(COOC2H5)2. 
Benzal-malonic  Ester. 

(2)  CH3.CHO  +  RNH2  ->  CH3CH  :  NR  +  H20. 
CH3CH  :  NR  +  CH2(COOC2H5)2  -> 

CH3CH  :  C(COOC2H5)2  +  NH2R. 
Ethylidene-malonic  Ester. 

C9H7N 

(3)  (CH3)2 :  CO  +  CH3.CO.CH2.COOC2H5 


(4)  (CH3)2CO 


(CH3)2C  :  C(COCH3)COOC2H5. 
Isopropylidine  Aceto-acetic  Ester. 


yCN 

/CH.COOC2H5 
(CH3)2 :  C<^ 


CH.COOC2H5 
\CN. 

Peeparation  69. — Ethyl  Cinnamate  (Ethyl  ester  of  3-phenyl-2-propen 
acid). 

C6H5CH  :  CH.COOC2H5.       CnH1202.  176. 

To  50  gms.  (excess)  of  pure  ethyl  acetate  (see  Preparation  196)  are  added 
23  gms.  (excess)  of  sodium  in  the  form  of  wire.  The  flask  is  cooled  in  ice, 
and  with  slight  shaking,  10  gms.  (1  mol.)  of  benzaldehyde  are  gradually 
added.  When  all  the  sodium  has  gone  into  solution,  the  flask  is  set  aside 
for  2  hours,  when  it  is  acidified  with  dilute  acetic  acid.  The  ester  layer 
which  separates  is  removed,  shaken  up  with  dilute  sodium  carbonate 
solution,  and  dried  over  calcium  chloride.  It  is  then  distilled,  the  fraction 
265°— 275°  being  retained. 

C2H5ONa 

C6H5CHO  +  CH3COOC2H5  >  C6H5CH  :  CH.COOC2H5. 

Colourless  liquid  ;  insoluble  in  water  ;  B.P.  271°.    (B.,  23,  976.) 

This  method  of  preparation  can  be  applied  generally  to  the  esters  of  the 
phenyl- olefine  acids.  Although  metallic  sodium  is  used,  yet  as  in  the 
aceto-acetic  ester  synthesis  (see  Reaction  XL VI.)  a  trace  of  alcohol  must 
always  be  present  to  form  sodium  ethoxide.  This  is  usually  the  case.  If 
necessary,  sodium  ethoxide  itself  can  be  employed.  The  use  of  some 
other  condensing  agents  will  be  clear  from  the  following  preparation. 

Preparation  70. — Benzalmalonic  Ester  (2-Benzylidene-propan  di-acid.) 

C6H5CH  :  C(COOC2H5)2.       C14H1604.  248. 
8  gms.  (1  mol.)  of  pure  drv  malonic  ester,  and  5  gms.  (1  mol.)  of  dry, 


CARBON  TO  CAKBON 


139 


freshly  distilled  benzaldehyde  are  mixed.  They  can  be  condensed  with 
hydrochloric  acid  gas  or  ammonia,  according  to  the  following  methods  : — 

(i.)  Hydrogen  Chloride. — The  mixture  is  cooled  to  —  10°  (see  p.  10) 
and  saturated  with  dry  hydrogen  chloride,  the  temperature  being  kept 
below  —  5°.  The  whole  is  then  allowed  to  stand  at  room  temperature  for 
8  days,  and  the  product  worked  up  as  described  below. 

(ii.)  Ammonia. — The  mixture  is  allowed  to  stand  with  2  gms.  of 
ammonia  in  alcoholic  solution,  until  all  the  benzaldehyde  has  disappeared. 

The  product  in  each  case  is  washed  with  much  water,  with  dilute  hydro- 
chloric acid  (especially  in  (ii.)  )  and  again  with  water.  It  is  then  dried 
over  anhydrous  sodium  sulphate  and  distilled  under  reduced  pressure,  the 
fraction  185° — 195°  at  12  mms.  being  retained. 

Hydrochloric  acid  acts  directly  as  a  condensing  agent.  With 
ammonia  the  reaction  may  be  formulated — 

C6H5CHO  +  NH3  — >  C6H5CH  :  NH  +  H20. 
C6H5OH  :  NH  +  CH2(COOC2H5)2  ->  C6H5CH  :  C(COOC2H5)2  +  NH3. 

Colourless  oil ;  insoluble  in  water ;  B.P.  13  198°.  (A.,  268,  156 ; 
D.R.P.  97734.) 

Compare  this  preparation  with  that  of  benzal  malonic  acid  (Preparation 
51). 

Preparation  71— Methylene-dimalonic  Ester. 

CH2[CH(COOC2H5)2]2.       C15H2408.  332. 

32  gms.  of  ethyl  malonate  and  8  gms.  of  formalin  (40%)  are  placed  in 
a  flask,  cooled  by  immersion  in  ice,  and  0-5  gm.  of  diethylamine  added. 
The  flask  is  then  cooled  and  left  to  stand  for  12  hours  at  room  temperature, 
after  which  it  is  heated  on  a  boiling  water  bath  for  5 — 6  hours.  The 
aqueous  layer  is  separated,  and  the  residue  distilled  under  reduced  pres- 
sure (about  12  mms.).  The  distillation  is  conducted  slowly,  so  that  all  the 
water  passes  over  below  50°.  Methylene-dimalonic  ester  passes  over  at 
190°— 200°. 

CH20  +  2HN(CaH5)a->  CHa(NCaH6)2  +  H20. 

/CH(COOC2H5)2 

CH2(NC2H5)2  +  2CH2(COOC2H5)2^  CH2<  +  2HN(C2H5)2. 

\CH(COOC2H5)2 

Yield. — 80%  theoretical  (27  gms.).  Colourless  oil ;  insoluble  in  water  ; 
B.P.  18,  205°  ;  B.P.  12,  198°.    (B.,  22,  3294  ;  31,  738,  2585.) 

Preparation  72. — Ethylidenebisaceto-acetic  Ester  (4-Methyl-2-6- 
dioxy-3-5-carbethoxyl-heptan) . 

CH3.CO.CH.CH(CH3)CH.(COOC2H5)CO.CH3 

j 

COOC2H5.  C14H2206.  286. 

8-5  gms.  (1  mol.)  of  pure  freshly  distilled  acetaldehyde  are  slowly  added 
to  50  gms.  (2  mols.)  of  pure  vacuum  distilled  cooled  aceto-acetic  ester  con- 
tained in  a  thick- walled  flask  closed  by  a  cork  and  having  a  thermometer 
reaching  almost  to  the  bottom.    The  flask  is  cooled  to  —  10°  to  —  15°  in 


140  SYSTEMATIC  ORGANIC  CHEMISTEY 


a  freezing  mixture  of  ice  and  salt.  A  few  drops  of  diethylamine  are  then 
added  by  means  of  a  burette.  Owing  to  neutralisation  of  the  first  portions 
of  the  amine  by  traces  of  acids  nearly  always  present  as  impurities,  an 
increase  in  the  temperature  seldom  takes  place  at  first.  After  the  addition 
of  about  5  drops  an  elevation  of  a  few  degrees  will  be  noticed,  and  the 
liquid  becomes  turbid.  From  this  point  a  further  5  drops  are  added 
slowly,  and  the  temperature  is  allowed  to  rise  gradually  to  0°.  20  more 
drops  are  then  slowly  added  with  frequent  shaking  ;  the  whole  operation 
should  take  about  1  hour.  In  all,  30  drops  (=1-5  gms.)  of  the  base  are 
required. 

The  whole  is  allowed  to  stand  in  the  freezing  mixture  for  15  minutes, 
then  removed  and  allowed  to  come  to  room  temperature.  Should  the 
temperature  go  up  to  20°  on  account  of  secondary  reactions,  the  flask  is 
cooled  for  a  short  time  in  ice-water. 

The  reaction  product  is  a  viscous  bright  yellow  liquid  in  which  numerous 
drops  of  water  are  suspended.  It  is  allowed  to  remain  until  it  solidifies  to 
a  crystalline  mass  ;  this  generally  requires  from  2 — 3  days. 

If  the  pure  product  is  required,  the  mass  is  pressed  on  a  porous  plate 
and  recrystallised  from  dilute  alcohol.  The  crude  product  will  serve  for 
the  preparation  of  dimethylcyclohexanone  (see  p.  77).  The  solidifica- 
tion of  the  crude  product  may  be  hastened  by  seeding  it,  after  one  day's 
standing,  with  crystals  obtained  in  a  previous  preparation.  This  is  best 
done  on  the  upper  portion  of  the  flask,  which  is  only  moistened  by  the 
liquid. 

CH3.CHO  +  2HN(C2H5)2  =  CH3CH(N(C2H5)2)2  +  H20. 

CH3 

CH3.CO.CHH        +         CH  +  HCH.CO.CH3 

COOC2H5  /\  I 

N(C2H5)2   N(C2H5)2  COOC2H5 
=    CH3  CH3 

CO  CO 

I  CH3       I       +  2NH(C2H5)2. 

CH  CH  CH 

I  I 
COOC2H5  COOC2H5 

Yield.—70%  theoretical  (40  gms.).  Colourless  needles  ;  M.P.  79°— 80°. 
(A.,  323,  83  ;  332,  1  ;  B.,  36,  2118.) 

Acetaldehyde  and  aceto-acetic  ester  in  presence  of  acetic  anhydride, 
hydrochloric  acid,  ammonia,  diethylamine,  piperidine,  etc.,  can  also  be 
made  to  yield  ethylidene  monoaceto-acetic  ester.  (A.,  218,  172  ;  B.,  29, 
172  ;  31,  735.) 

With  regard  to  the  intermediate  compounds  of  the  types  RCH  :  NR  and 
RCH  :  (NRRX)2  postulated  in  some  of  the  above  reactions,  it  is  to  be  noted 
that  compounds  of  the  type  RCH(OH)NHR  and  RCH(OH)NRR1  can  also 
be  regarded  as  intermediates. 

Reaction  XLVI.  Condensation  of  an  Ester  with  itself  or  with  another 
Ester  by  means  of  Sodium  Ethoxide,  or  Sodamide  (Glaisen).    (J.  (1868), 


CARBON  TO  CARBON 


141 


323  ;  Phil.  Mag.,  156,  37  ;  A.,  186,  161,  214  ;  201,  243  ;  213,  137.)- 
When  sodium  ethoxide  or  sodamide  acts  on  acetic  or  propionic  esters, 
2  mols.  of  the  esters  condense  to  yield  aceto-acetic  or  propiopropionic 
esters  respectively.  In  the  reaction  1  mol.  of  alcohol  is  split  off  from 
2  mols.  of  ester,  the  ethoxy  group  coming  from  one  molecule,  and  the 
hydrogen  atom  from  the  a-carbon  of  a  second. 

CH3 

CH3CH2.COO.C2H5  +     |  C2H5ONa 

HCH.COOC2H3  > 

CH3CH2CO.CH(CH3)COOC2H5  +  C2H5OH. 

The  reaction  can  also  be  extended  to  condensations  between  two 
different  esters,  it  being  only  necessary  that  one  of  the  esters  should  have 
two  a-hydrogen  atoms,  one  to  react  and  one  to  enable  a  sodio-derivative 
to  be  formed.  /3-ketonic  compounds  always  result — this  condensation  in 
fact  belonging  to  the  same  class  as  those  described  in  Reaction  XXIII.  (6). 
The  higher  esters  do  not  condense  in  the  same  manner.  When  sodium 
acts  on  normal  butyric  ester,  ^so-butyric  ester,  iso- valeric  ester,  etc.,  the 
resulting  compounds  are  not  analogous,  being  hydroxy-alkyl  derivatives 
of  higher  fatty  acids  (A.,  249,  54).  Some  di-basic  esters  in  undergoing 
the  condensation  yield  ring  compounds  ;  this  is  an  especially  important 
feature  of  the  reactions  (see  p.  142). 

The  mechanism  of  the  process  must  now  be  considered.  The  reaction 
between  metallic  sodium  and  acetic  ester  only  occurs  in  the  presence  of  a 
trace  of  alcohol  (B.,  3,  305),  so  sodium  ethoxide  must  be  regarded  as  the 
condensing  agent  (cf.  Reaction  XLV.,  p.  137).  This  view  is  supported 
by  the  fact  that  separately  prepared  sodium  ethoxide  gives  almost  as 
good  a  yield  as  metallic  sodium. 

The  first  step  in  the  synthesis  may  be  taken  to  be — 

xOC2H5  CH2 
CH3 :  CO.OC2H5  +  C2H5ONa  ->  CH3C-ONa         or  c.0C2H5 

\OC2H5  ONa 
I.  II. 

II.  results  from  I.  by  the  loss  of  alcohol,  but  I.  is  more  probably  the 
intermediate  compound,  because  methyl  benzoate  and  sodium  benzoxide 
give  the  same  compound — actually  isolated — as  benzyl  benzoate  and 
sodium  methoxide. 

/ONa 

C6H5COOCH3  +  C6H5CH2ONa->C6H5C-OCH3 

y  \OCH2C6H5. 
C6H5COOCH2C6H5  -fCH3ONaX 

I.  then  reacts  with  the  still  unchanged  ester  or  with  a  molecule  of  the 
other  ester — 

CHov       -OC2H5  H\ 

\c/  +     >C(R)COOC2H5   > 

NaO/    \OC2H5  H/ 

CH3C  :  C(E)COOC2H5  +  2C2H5OH. 

I 

ONa 


142  SYSTEMATIC  ORGANIC  CHEMISTRY 

or  else  a  molecule  of  ester  and  a  molecule  of  II.  unite  and  then  split  off 
alcohol,  with  rearrangement. 

OC2H5  CH2 
CH2(R)C/'  ,  cqC2H 


2XX5 


ONa 
CH2 


CH2(R)C<   0    COC2H5   > 

xONa 

/OC2H5  — C2H6OH 

RCH2C<  CH2  — COC2H5  > 

\ONa  |i 
0 

RCHC  =  CH— COC2H5. 

!  II 

ONa  0 

(A.,  297,  92  ;  B.,  36,  3678  ;  38,  714,  1934.)  Both  assumptions  coincide 
equally  well  with  the  fact  that  fatty  acid  esters  do  not  condense  analogously 
to  the  above,  with  secondary  and  tertiary  alkyl  groups. 

Sodamide  can  also  be  employed  as  condensing  agent.  The  intermediate 
compound  is  then — 

CH3  v     /OC2H5  CH2^ 
I.  >C<  or         >C— OC2H5.  II. 

NaCK     \NH2  NaCK 

It  is  in  favour  of  II.  that  it  is  an  intermediate  compound  independent  of 
the  condensing  agent.  For  the  influence  of  solvents  on  the  reaction,  see 
C,  (1907),  IL,  30. 

The  following  examples  are  of  interest : — 

C2H5ONa 

(i.)  H.COOC2H5  +  CH3.COOC2H5  > 

H.CO.CH2COOC2H5  +  C2H5OH. 

X 

Formylacetic  Ester. 
(Hydroxym ethylene- acetic  Ester). 

The  above  reaction  goes  best  in  ethereal  or  benzene  solution. 

COOC2H5  C2H5O.CO.CO.CH2.COOC2H5. 
(ii.)     |  +  CH3.COOC2H5  ->  Oxalacetic  Ester 

COOC2H5  +  C2H5OH. 

COOC2H5  /CHaCOOCaH5 
Ciii.)  I  +  C  :  (CH3)2  -> 

COOC2H5  \H2COOC2H5 

/3-/3-Di-methylglutaric-di-ethyl-ester. 
CO  CHCOOC2H5 

^>C(CH3)2 

CO  CHCOOC2H5. 

Di  ketocamphopyric  Ester. 

This  is  an  important  step  in  the  synthesis  of  camphor  (see  Reactions 
XLIV.  (6)  (3) ). 


CARBON  TO  CARBON 


143 


Preparation  73. — Aceto-acetic  Ester  (Ethyl  ester  of  3-oxy-butan  acid). 

CH3COCH2COOC2H5  or  CH3C(OH) :  CH.COOC2H5.     C6H10O3.  130. 

250  gms.  of  commercial  ethyl  acetate  are  shaken  with  sodium  carbonate 
solution,  separated  and  allowed  to  stand  for  24  hours  over  freshly  fused 
calcium  chloride,  filtered  into  a  distilling  flask,  and  redistilled,  care  being 
taken  that  all  parts  of  the  apparatus  are  perfectly  dry.  This  treatment 
frees  the  ethyl  acetate  from  all  traces  of  acetic  acid  and  water,  but  leaves 
enough  alcohol  to  allow  sodium  ethoxide  to  be  formed  to  bring  about  the 
reaction.  With  too  much  alcohol  the  reaction  goes  too  vigorously  and 
the  yield  is  poor,  with  too  little  the  reaction  goes  very  slowly  or  not  at  all. 

20  gms.  (1  atom)  of  pure  dry  sodium  in  the  form  of  wire  are  placed  in 
a  clean  dry  J-litre  round-bottomed  flask.  The  latter  is  attached  to  a  long 
reflux  condenser,  and  200  gms.  (excess)  of  the  purified  ethyl  acetate  are 
slowly  introduced  through  the  top  of  the  condenser.  When  the  first 
action  is  over,  the  whole  is  heated  on  a  water  bath  to  gentle  ebullition  for 
3  hours,  when  150  gms.  of  50%  acetic  acid  are  added  gradually  till  the 
mixture  is  just  acid  (test  with  litmus).  The  whole  is  well  shaken  to  re- 
dissolve  any  deposited  solid,  and  the  mixed  ethyl  acetate  and  ethyl  aceto- 
acetate  separated  by  adding  an  equal  volume  of  saturated  brine.  Should 
a  precipitate  separate  a  little  water  is  added  to  dissolve  it.  The  upper 
layer  of  the  mixed  esters  is  fractionally  distilled  under  reduced  pressure, 
the  fraction  85° — 95°  at  40  mms.  separately  collected  and  redistilled  under 
reduced  pressure.  The  residue  in  the  flask  contains  dehydracetic  acid 
(see  Preparation  63).  To  obtain  the  best  results  the  experiment  must  be 
completed  in  one  day. 

/OC2H5 

C2H5.ONa  +  CH3.COOC2H5  =  CH3.C— OC2H5 

\O.Na. 

/OC2H5 

CH3.C— OC2H5  +  CH3.COOC2H5  = 
\ONa 

CH3.C  :  CHCOOC2H5  +  2C2H5.OH. 
O 

Na 

CH3.C  :  CHCOOC2H5  +  CH3.COOH  = 
ONa 

CH3.C  :  CHCOOC2H5  +  CH3.COONa 
OH 

CH3.C :  CHCOOC2H5    ->*  CH3.CO.CH2.COOC2H5. 
OH 

Yield. — 40%  theoretical  (44  gms.).  Colourless  pleasant-smelling  liquid  ; 
slightly  soluble  in  water  ;  B.P.  760  181°  ;  B.P.  12  72°  ;  D.  24°  1-0256. 

For  the  estimation  of  the  amount  of  keto  and  enol  forms  present  in  the 
equilibrium  mixture,  see  p.  493. 


144  SYSTEMATIC  OKGANIC  CHEMISTRY 


For  the  separation  of  the  keto  and  enol  forms  by  distillation,  see  B.,  53, 
1410.    (J.,  (1863),  323  ;  Phil.  Trans.,  156,  37  ;  A.,  186,  161,  214.) 

Reaction  XLVII.  Condensation  of  an  Ester  with  itself  by  the  action  of 
Iodine  on  its  Sodio  Derivative.  (B.,  23  ;  R.,  141 ;  A.,  201, 144  ;  266,  88.)— 
When  iodine,  usually  in  ethereal  solution,  acts  on  the  sodio  derivatives  of 
esters,  such  as  malonic  or  aceto-acetic  esters,  the  metal  is  eliminated,  and 
higher  dibasic  esters  are  obtained.  As  will  be  seen,  the  reaction  is  especially 
useful  for  preparing  cyclo-paraffins  by  acting  with  iodine  (or  bromine) 
upon  disodio-methylene-  and  disodio-ethylene-,  etc.,  di-malonic  esters. 


(a) 


COOC2H5 

HC  +  I2  +     HC  -> 

I!  II 
C.ONa  C.ONa 

I  I 
OC2H5  OC2H5 

H  H 

C  C  :  (COOC2H5)2 

(COOC2H5)2 
Ethane -tetra  carboxylie  Ester 
(Di-malonic  Ester.) 

/CNafCOOCgHs),  /C(COOC2H5)2 
{h)         CH2  +I2    ->   CH2  J 

m  ^CNafCOOCaHgk    ,  \j(COOC2H5)2. 
Disodio-methylene  di-malonic  Ester      Cyclo -propane  tetra- 
(Propane-tetracarboxylic  Ester.)  carboxylie  Ester. 

//CH2CNa(COOC2H5)2 

W  CH2  +I2  > 

\CH2CNa(COOC2H5)2 
Disodio  propylene  di-malonic  Ester 
(Pentane  tetracarboxylic  Ester.) 

/CH2.C(COOC2H5)2 
CH2  i 

\CH2.C(COOC2H5)2. 
Cyclo -pentane  tetracarboxylic  Ester. 

Cf.  Reaction  XLIV.  (a)  (3). 

W  2CH3.CO.CHNaCOOC2H5  +  I2 

->    CH3CO  CHCOOC2H5 

CH3.CO.CH.COOC2H5. 
Di-acetosuccinic  Ester. 

The  action  of  methylene  and  ethylene  iodides,  etc.,  on  the  sodio  deriva- 
tives of  the  esters  dealt  with  above  might  have  been  discussed  under 
Reaction  XLIV.  (a),  but  is  best  dealt  with  here.  The  di-iodides  react 
analogously  to  the  iodine  molecule  ;  extra  carbon  is  of  course  introduced 
into  the  reacting  molecules.    The  following  will  illustrate  :— 


CARBON  TO  CARBON 


145 


/HC(COOC2H5)2 
(i.)  2CHNa(COOC2H5)2  +  CH2I2  ->  CH2 

\HC(COOC2H5)2 
C(COOC2H5)2 


(ii.)  NaC(COOC„H5)2 

/  IHaC 


CH, 


NaC(COOCaH5)j 


CH2 

C(COOC2H5)2 

(iii.)    2CH3COCHNaCOOC2H5  +  CH  J2  -> 

CH3COCHCOOC2H5  CH8COCCOOC2H5 

i  /\ 
H2C  C2H5ONa  +  CH2I2       H2C  CH2 

I   > 


CH3.COCHCOOC2H5  CH3CO  C  COOC2H5 

It  will  be  seen  that  whereas  iodine  leads  to  1  :  2  tetra-  and  di-basic 
esters,  methylene,  ethylene,  etc.,  iodides  yield  respectively  1:3,  1:4, 
etc.,  esters.  The  yields  in  these  ring  syntheses,  as  in  most  others,  vary  in 
agreement  with  Baeyer's  "  Strain  Theory." 

Preparation  74. — Diethyl  Di-acetosuccinate  ( 1.2-Dicarbethoxyl-l :  2- 
diethanoyl  ethan). 

CH3.COCH— CH.CO.CH3.       C12H1806.  258. 

I    -  I 
C2H5OOC  COOC2H5. 

In  a  stoppered  bottle  of  500  c.cs.  capacity  provided  with  a  reflux  con- 
denser, 25  gms.  (2  mols.)  of  aceto-acetic  ester  are  dissolved  in  150  gms.  of 
pure  ether  which  has  been  dried  over  sodium,  and  to  this  solution  5  gms. 
(2  mols.)  of  fine  sodium  wire  are  added.  After  2  hours,  the  bottle  is 
shaken  at  intervals,  being  stoppered  while  so  doing,  till  no  further 
evolution  of  hydrogen  takes  place,  and  all  the  metal  has  been  con- 
verted into  sodio-aceto-acetic  ester.  20  gms.  (excess)  of  finely  powdered 
iodine  are  dissolved  in  pure  anhydrous  ether,  and  the  solution  added  in 
small  portions,  and  with  constant  shaking  to  the  solution  of  the  sodio- 
aceto-acetic  ester.  Sodium  iodide  is  precipitated  as  soon  as  the  colour 
of  the  iodine  no  longer  vanishes  at  once,  the  solution  is  filtered,  the 
ether  evaporated  off,  and  the  di-acetsuccinic  ester  allowed  to  solidify. 
It  is  then  pressed  on  a  porous  tile,  and  recrystallised  from  warm  50% 
acetic  acid. 

2Na  I2 
2CH3CO.CH2COOC2H5   >    2CH3C(ONa)  :  CHCOOC2H5   > 

CH3.CO.CH  —  CH.CO.CH3 
C2H5OOC  COOC2H5. 

Yield. — 40%  theoretical  (10  gms.).  Colourless  crystals  ;  plates  when 
crystallised  slowly  ;  needles  when  crystallised  rapidly  ;  soluble  in  ether  ; 
insoluble  in  water  ;  M.P.  88°.    (B.,  7,  892  ;  A.,  266,  88.) 

(Cf.  Reaction XXXVII.;  which  is,  so  to  speak,  converse  to  this  reaction.) 

s.o.c.  l 


CHAPTER  VIII 


carbon  to  carbon 

Nitrogen  Compounds 

Nitrogen  enters  into  the  constitution  of  many  carbon  compounds,  and 
such  nitrogen-containing  compounds  are  usually  very  reactive ;  in 
addition  to  reacting  with  other  compounds  a  great  number  readily  undergo 
intramolecular  transformations.  Nitrogen  also  plays  an  important  part 
in  ring  formation  ;  nitrogen-containing  rings  are  very  stable,  and  the 
condensations  which  give  rise  to  them  many  and  various.  On  this 
account  a  great  many  important  reactions  and  preparations  come  to 
be  dealt  with  in  this  section  ;  of  these,  however,  only  a  small  selection 
can  be  given. 

Reaction  XLVIII.  {a)  Action  of  Alkali  Cyanides  on  Alkyl  and  Acyl 
Halides.  (Bl.,  [2],  50,  214.) — This  reaction  is  capable  of  very  wide 
application,  all  the  simple  alkyl  halogen  compounds,  the  acyl  halides,  and 
the  halogen  fatty  acids  come  within  its  scope.  The  nitriles  so  formed 
yield  acids  by  hydrolysis,  so  it  is  frequently  the  first  step  in  the  synthesis 
of  an  acid — the  preparation  and  hydrolysis  of  the  nitrile  are  often  com- 
bined. The  preparations  of  malonic,  succinic,  tricarballylic  and  other 
acids  (Preparations  58,  59,  116,  60)  illustrate  this.  The  extension  of 
this  reaction  to  acyl  halides  is  important,  and  should  be  referred  to,  as 
should  the  interaction  of  silver  cyanide,  and  alkyl  iodides,  to  give 
isonitriles.  Mercuric  and  silver  cyanides,  it  may  be  noted,  give  with 
acyl  chlorides  and  bromides  better  yields  of  normal  acyl  nitriles  than  do 
the  alkali  cyanides. 

In  reactions  where  nitriles  are  prepared  from  halogen  compounds 
by  double  decomposition  with  alkali  cyanide  in  alcoholic  or  aqueous 
alcoholic  solution,  the  latter  is  usually  added  in  solution  or  as  a  powder 
(cf.  Preparations  75,  76,  77),  otherwise  the  alkali  halide  which  separates 
forms  a  coating  round  the  cyanide  and  hinders  further  action.  If  the 
reaction  is  performed  in  aqueous  solution,  as  in  the  preparation  of  malonic 
acid  (p.  119),  this  precaution  is  not  so  necessary  ;  the  alkali  halide,  when 
formed,  remains  in  solution. 

Preparation  75. — Ethylene  Di-Cyanide  (Succino-nitril). 

CH2.CN 

|  C4H4N2.  80. 

CH2.CN. 

The  solution  of  the  nitrile  prepared  as  in  Preparation  59  from  100  gms. 
(1  mol.)  of  ethylene  dibromide  and  75  gms.  (excess)  of  potassium  cyanide, 
after  filtration  from  the  separated  potassium  bromide,  is  evaporated  on  a 

146 


CARBON  TO  CARBON 


147 


water  bath  under  reduced  pressure.  The  residue  is  extracted  with 
absolute  alcohol,  the  extract  evaporated  as  before,  and  the  residue 
fractionated  under  reduced  pressure,  the  fraction  144° — 150°  at  10  mms. 
being  retained. 

CH2Br  CH2CN 

|  +  2KCN  =  |  +  2KBr. 

CH2Br  CH2CN 

Yield. — 80%  theoretical  (34  gms.).  Amorphous  transparent  mass  ; 
readily  soluble  in  water,  chloroform  and  alcohol ;  sparingly  soluble  in 
ether  ;  M.P.  54-5°  ;  B.P.  10  147°  ;  B.P.  20  159°.  (Bl.,  [2],  50,  214  ;  C, 
(1901),  II.,  807.) 

Propenyl  tricyanide,  the  nitrile  of  tri-carballylic  acid,  is  obtained  in  a 
similar  manner  (see  Preparation  60). 
Prepaeation  76. — Benzyl  Cyanide  (Phenyl-ethan  Acid  Nitril). 

C6H5.CH2.CN.       C8H7N.  117. 

60  gms.  (slightly  more  than  1  mol.)  of  commercial  potassium  cyanide 
are  dissolved  in  55  gms.  of  water  in  a  f -litre  round-bottomed  flask  fitted 
with  a  reflux  condenser  and  placed  in  a  fume  cupboard.  100  gms.  (1  mol.) 
of  benzyl  chloride  dissolved  in  100  gms.  of  alcohol  are  poured  slowly  into 
the  hot  solution  of  potassium  cyanide  through  the  top  of  the  condenser, 
and  the  whole  gently  boiled  for  4  hours  on  a  sand  bath.  The  flask  is  then 
cooled,  and  the  upper  dark  brown  liquid,  consisting  of  an  alcoholic  solution 
of  benzyl  cyanide,  is  decanted  from  the  crystalline  deposit  of  potassium 
chloride  and  distilled  over  wire  gauze  in  a  fume  cupboard,  the  fraction 
210°— 235°  being  retained.  It  is  crude  benzyl  cyanide,  and  can  be  used 
for  Preparation  173. 

To  prepare  the  pure  substance,  this  fraction  is  redistilled  and  collected 
at  230°— 235°. 

C6H5CH2C1  +  KCN  ■-=  C6H5CH2CN  +  KC1. 

Yield. — Almost  theoretical  (55  gms.).  Colourless,  pungent  smelling 
liquid  ;  B.P.  232°  ;  D.  l74-5  1-0171.    (A.,  96,  247  ;  B.,  14,  1645  ;  19,  951.) 

Reaction  XLVIII.  (b)  Action  of  Alkali  Cyanides  on  Alkyl  Halogen 
Sulphates.  (A.,  10,  249.) — The  alkyl  nitriles  may  also  be  prepared  by 
dry-distilling  alkali  cyanides  with  alkali-alkyl-sulphates. 

MXCN  +  S02(OMn)OR  =  RCN  +  S02(OM11)(OM1). 
Pkepaeation  77. — Ethyl  Cyanide  (Propionitril). 

C2H5CN.       C3H5N.  55. 

50  gms.  (excess)  of  finely  powdered  (caution!),  dry,  commercial  potas- 
sium cyanide  and  50  gms.  (1  mol.)  of  finely  powdered  potassium  ethyl 
sulphate  dried  at  100°  are  intimately  mixed.  An  iron  tube,  closed  at  one 
end,  is  one-third  filled  with  the  mixture.  The  tube  is  tapped  while  in  a 
horizontal  position  to  form  a  channel  along  the  upper  surface  of  the 
mixture,  is  placed  in  a  combustion  furnace  so  that  the  open  end  projects 
3  cms.  from  the  furnace,  and  connected  with  a  condenser  and  receiver,  all 

L  2 


148 


SYSTEMATIC  ORGANIC  CHEMISTRY 


being  set  up  in  a  fume  cupboard.  The  mixture  is  then  gradually  heated, 
from  the  front  backwards,  to  a  red  heat.  The  distillate  is  redistilled  to 
110°,  and  the  second  distillate  (propionitril,  isopropionitril,  alcohol  and 
water)  shaken  with  a  small  quantity  of  cone,  hydrochloric  acid  to  remove 
isopropionitril,  washed  with  a  small  quantity  of  water,  dehydrated  over 
calcium  chloride  or  anhydrous  potassium  carbonate  and  fractionated 
between  97°  and  101°.  The  propionitril  dissolved  in  the  washings  is 
separated  by  adding  calcium  chloride,  and  worked  up  as  above. 

C2H5.O.S02.OK  +  KCN  =  KO.S02.OK  +  C2H5CN. 

7^.-60%  theoretical  (10  gms.).  Colourless  liquid,  peculiar  ethereal 
smell ;  slightly  soluble  in  water  ;  B.P.  98°  ;  D.  \2  0-789.  (A.,  10,  249  ; 
148,252;  159,79.) 

A  somewhat  similar  method  of  cyanide  preparation  is  applicable  in  the 
aromatic  series  ;  aromatic  sulphonic  acid  potassium  salts,  on  fusion  with 
potassium  cyanide  or  potassium  ferrocyanide,  yield  aromatic  nitriles. 
The  reaction  can  be  extended  to  derivatives  of  pyridine. 


S03K  I      I CN 

+  KCN  =||        +  K2SO. 


N  N 

(Nicotino  -nitrile.) 

Reaction  XLVTII.  (c)  Action  of  di-methyl  Sulphate  on  Potassium 
Cyanide.  (B.,  40,  3215.) — This  method,  which  gives  excellent  yields,  is 
only  applicable  to  the  preparation  of  aceto-nitrile  ;  dimethyl  sulphate  is 
unique  in  this  as  in  other  reactions. 

Pkepaeation  78. — Methyl  Cyanide  (Acetonitril). 

CH3CN.      C2H3N.  41. 

68  gms.  (1  mol.)  of  finely  powdered  potassium  cyanide  are  dissolved  in 
60  c.cs.  of  water,  in  a  500-c.c.  round-bottomed  flask,  and  after  cooling, 
126  gms.  (1  mol.)  of  dimethyl  sulphate  (caution !  see  p.  254)  are 
added  in  three  equal  portions,  the  whole  being  shaken  vigorously  and 
cooled  under  water  after  each  addition.  During  the  shaking,  the  flask  is 
closed  by  a  one-holed  cork  carrying  a  glass  tube  bent  three  or  four  times, 
so  as  to  form  a  spiral,  having  its  axis  horizontal.  This  prevents  spurting 
out  of  any  liquid.  The  milky  liquid  is  distilled  on  a  water  bath  in  a  fume 
cupboard  at  82°,  a  litre  flask  being  used  owing  to  frothing.  The  residue 
in  the  flask  is  treated  on  cooling  with  another  65  gms.  (1  mol.)  of  potassium 
cyanide,  added  slowly,  in  50%  solution  as  before,  and  the  whole  is  very 
cautiously  distilled  from  a  water  bath.  A  violent  reaction  occurs,  and 
when  this  has  slackened,  the  distillation  is  continued  until  the  residue  in 
the  flask  becomes  solid  and  nothing  more  comes  over.  The  distillate  is 
diluted,  and  shaken  with  half  its  volume  of  water ;  solid  potassium  car- 
bonate is  added  until  no  more  dissolves,  the  layer  of  nitrile  is  separated 
from  the  aqueous  solution  and  redistilled  over  phosphorus  pentoxide,  the 
fraction  79° — 83°  being  retained. 


CAKBON  TO  CARBON 


149 


KCN  +  (CH3)2S04  =  (CH3)KS04  +  CH3CN. 
CH3KS04  +  KCN  =  K2S04  +  CH3CN. 

Yield. — 95%  theoretical  (78  gms.).  Colourless  liquid  ;  ethereal  odour  ; 
slightly  soluble  in  water  ;  B.P.  82°.    (B.,  40,  3215.) 

Reaction  XLIX.  (a)  Action  of  Cuprous  Potassium  Cyanide  on  Aromatic 
Diazonium  Compounds.  (Sandmeyer).  (B,,  17,  1633,  2650;  18,  1492, 
1496.) — If  a  diazonium  salt  is  added  to  a  hot  solution  of  cuprous-potassium 
cyanide,  and  the  whole  boiled  on  a  water  bath,  nitrogen  is  evolved,  and 
the  corresponding  nitrile  formed. 

2R.N2C1  +  KCN(CuCN)2  ->  2RCN  +  2N2  +  KCN  +  Cu2Cl2. 

As  usual  in  Sandmeyer  reactions,  the  product,  if  volatile,  is  separated  by 
distillation  in  steam  ;  if  non- volatile,  extraction  or  nitration  is  used.  The 
manner  in  which  the  cuprous  salt  reacts  is  not  exactly  known  ;  it  certainly 
unites  at  first  with  the  diazonium  compound  to  form  a  double  salt  (cf. 
Reaction  CLXVL).  The  method  is  widely  applicable,  and  as  the  yields 
are  usually  good,  it  is  a  standard  method  for  the  preparation  of  aromatic 
nitriles. 

Preparation  79. — Benzo-nitrile  (Cyano-benzene). 

C6H5.CN.       C7H5N.  103. 

The  details  of  this  preparation  are  practically  the  same  as  those  given 
for  j9-tolu-nitrile  (Preparation  80) .  A  cuprous-potassium  cyanide  solution, 
prepared  as  therein  described,  is  warmed  to  about  70°,  and  added  in  small 
portions  to  a  solution  of  diazonium-benzene  chloride  prepared  from 
18-6  gms.  (1  mol.)  of  aniline  as  described  in  Preparation  378.  When  the 
addition  is  complete,  the  liquid  is  warmed  on  a  water  bath  for  15  minutes 
and  distilled  in  steam  ;  the  distillate  is  extracted  with  ether.  The 
ethereal  solution  is  washed  repeatedly  with  dilute  caustic  soda  and  with 
dilute  sulphuric  acid,  dried  over  anhydrous  potassium  carbonate,  filtered, 
and  the  oil  which  remains  on  driving  off  the  ether,  fractionated.  Owing 
to  the  evolution  of  cyanogen  and  hydrocyanic  acid,  this  preparation  must 
be  carried  out  in  a  good  fume  cupboard. 

HN02  Cu2CN2.KCN 

C6H5NH2  >  C6H5.N2.C1  >  C6H5CN. 

HC1 

Yield. — 65%  theoretical  (13  gms.).  Colourless  oil ;  odour  resembling 
that  of  benzaldehyde  or  nitrobenzene  ;  insoluble  in  water  ;  soluble  in 
ether  ;  B.P.  191°.    (B.,  17,  2653.) 

Preparation  80.  -^-Tolu-nitrile  (l-Methyl-4-cyano-benzene). 

CH3.C6H4.CN.[1.4.].  C8H7N.  117. 
50  gms.  (1  mol.)  of  copper  sulphate  crystals  are  dissolved  in  200  c.cs.  of 
water,  and  56  gms.  (excess)  of  96%  potassium  cyanide  added  to  the  warm 
solution.  As  cyanogen  is  evolved,  the  operation  must  be  carried  out  in  a 
good  fume  cupboard,  and  the  fumes  must  on  no  account  be  inhaled. 
20  gms.  (1  mol.)  of  ^-toluidine  are  then  diazotised  as  in  Preparation  378, 
and  the  diazo  solution  gradually  added  in  a  J  hour,  from  a  dropping  funnel 
to  the  cuprous-potassium  cyanide  solution  at  90°,  the  mixture  being  kept 


150  SYSTEMATIC  ORGANIC  CHEMISTRY 


well  shaken.  The  product  is  heated  on  a  water  bath  for  a  J  hour,  and 
distilled  in  steam  in  a  good  fume  cupboard,  since  hydrogen  cyanide  and  a 
little  isocyanide  are  formed  ;  the  solid  distillate  is  filtered  off,  dried  on  a 
porous  plate,  and  redistilled. 

CuS04  +  2KCN  =  Cu(CN)2  +  K2S04. 
2Cu(CN)2  =  Cu2(CN)2  +  (CN)2. 
Cu2(CN)2  +  KCN  2CuQN.KCN. 
2CH3.C6H4N2C1  +  2CuCN.KCN  =  2CH3.C6H4.CN  +  2N2  +  Cu2Cl2  +  KCN. 

Yield—  65%  theoretical  (14  gms.).  Colourless  crystals  ;  insoluble  in 
water;  soluble  in  ether  ;  M.P.  24°  ;  B.P.  218°.    (B.,  17,  2653.) 

o-Tolu-nitrile  is  prepared  in  an  exactly  similar  fashion  from  o-toluidine. 
It  boils  at  205°  ;  D.  °4  1-006. 

Reaction  XLIX.  (b)  Action  of  finely  divided  Copper  and  Alkali  Cyanides 
on  Aromatic  Diazonium  Compounds  (Gattermann).  (B.,  23,  1218.)— This 
is  the  Gattermann  modification  of  the  preceding  Sandmeyer  reaction ;  as 
usual,  the  cuprous  salt  is  replaced  by  finely  divided  copper.  This  method 
gives  better  yields  of  some  aromatic  nitriles. 

Preparation  81. — Benzonitrile  (Cyanobenzene). 

C6H5CN.       C7H5N.  103. 

(This  reaction  must  be  carried  out  in  a  good  fume  cupboard.) 

31  gms.  (1  mol.)  of  aniline  are  dissolved  in  40  gms.  (excess)  of  50%  sul- 
phuric acid,  the  solution  cooled  to  0°  by  addition  of  ice,  and  the  base 
diazotised  by  the  addition  of  23  gms.  (1  mol.)  of  sodium  nitrite  as  described 
in  Preparation  378.  80  gms.  (excess)  of  96%  potassium  cyanide  in  50% 
solution  are  poured  in,  and  then,  with  constant  stirring,  40  gms.  of  copper 
paste  (see  p.  504)  are  added  in  small  quantities,  and  the  whole  allowed 
to  stand  until  the  evolution  of  nitrogen  ceases  and  the  copper  sinks  to  the 
bottom  of  the  vessel.  The  reaction  is  then  over.  The  product  is  steam- 
distilled,  and  the  nitrile  extracted  and  purified  as  described  under  Pre- 
paration 79. 

C6H5N2S04H  +  KCN(Cu)  =  C6H5CN  +  KHS04  +  N2(Cu). 

Yield. — 60%  theoretical  (20  gms.).  Colourless  oil ;  insoluble  in  water  ; 
soluble  in  ether  ;  odour  resembling  that  of  benzaldehyde  or  nitrobenzene  ; 
B.P.  191°.    (B.,  23,  1218.) 

The  preparation  of  o-  or  ^-tolu-nitrile  is  exactly  similar. 

Reaction  L.  (a)  Addition  of  Hydrogen  Cyanide  to  Aldehydes  or  Ketones. 
(B.,  14,  235  ;  39,  1224,  1857  ;  28,  10  ;  C.  Z.,  (1896),  90.)— Hydrocyanic 
acid  adds  on  to  aldehydes  and  ketones  to  yield  a-hydroxy  nitriles  (Cyan- 
hydrins). 

KI^CO  +  HCN  ->  RRiCfOHjCN. 

Nascent  hydrogen  cyanide  formed  by  the  action  of  hydrochloric  acid  on 
potassium  cyanide  is  usually  employed  except  with  sugars,  where  hydro- 
cyanic acid  and  a  little  ammonia  are  used.  The  manner  in  which  am- 
monia promotes  the  action  as  also  the  better  results  obtained  by  the  use 
of  the  bisulphite  compound  of  the  aldehydes  and  potassium  cyanide  have 
been  dealt  with  under  Reaction  XXXVfll.  (c). 


CARBON  TO  CARBON 


151 


Preparation  62  illustrates  the  importance  of  this  reaction  in  the  sugar 
group.    For  the  hydrolysis  of  nitriles,  see  p.  232. 
Preparation  82.— Acetone  Cyanhydrin  (2-Hydroxy-2-cyano-propan). 

(CH3)2C(OH)CN.       C4H7ON.  85. 

10  gms.  (1  mol.)  of  acetone  are  shaken  with  a  saturated  sodium  bisul- 
phite solution  containing  18  gms.  (1  mol.)  of  NaHS03,  and,  after  cooling, 
30  gms.  (excess)  of  a  cold  50%  solution  of  96%  potassium  cyanide  are 
slowly  added.  The  crystalline  bisulphite  compound  soon  dissolves  and  a 
fluorescent  oil  is  formed.  This  is  extracted  several  times  with  ether,  and 
the  ethereal  extracts  are  shaken  with  saturated  bisulphite  solution  (to 
remove  acetone)  and  then  washed  with  saturated  brine.  The  ether  is 
removed  on  a  water  bath,  and  the  residual  oil  dried  under  reduced  pressure 
over  cone,  sulphuric  acid.  It  is  then  fractionated  under  reduced  pressure; 
the  fraction  80° — 85°  at  23  mms.  being  retained. 

OH 


(CH3)2CO  +  NaHS03  =  (CH3)2CX 

\OS02Na 

ATT  OTT 

(CH<O.SO,Na  +  ^  =  (CH<CN  +  KNaSo3. 

Yield. — 96%  theoretical  (15  gms.).  Colourless  odourless  liquid  ;  in- 
soluble in  water  ;  soluble  in  ether  ;  B.P.  23  82°.  (B.,  39,  1225,  1857  ; 
Rec,  28,  10  ;  C.  Z.,  (1896),  90.) 

The  action  of  hydrogen  cyanide  on  the  aldehyde  itself,  and  the  action  of 
potassium  cyanide  on  the  bisulphite  compound,  are  directly  contrasted  in 
the  following  preparation. 

Preparation  83. — Mandelonitrile  ( (Phenyl)-(hydroxy)-(cyano)-methan) 

C6H5CH(OH)CN.       C8H7ON.  133. 

Method  I. — 14  gms.  (1  mol.)  of  finely  powdered  96%  potassium  cyanide, 
and  20  gms.  (1  mol.)  of  freshly  distilled  benzaldehyde  are  placed  in  a  flask 
cooled  with  ice  and  salt.  The  quantity  of  the  most  cone,  hydrochloric 
acid  available,  corresponding  to  7  gms.  (1  mol.)  of  anhydrous  acid  (about 
20  gms.  cone,  acid  will  be  required),  are  slowly  dropped  in  with  frequent 
shaking.  This  must  be  done  in  a  good  fume  cupboard.  The  whole  is 
allowed  to  stand  for  1  hour,  being  shaken  at  frequent  intervals  ;  it  is  then 
poured  into  5  volumes  of  water,  and  the  oil  which  separates  well  washed 
with  water  several  times  ;  a  further  purification  is  impossible  owing  to  its 
instability. 

C6H5.CHO  +  KCN  +  HC1  =  C6H5(OH)CN  +  KC1. 
Yield.— Theoretical  (26  gms.).    (B.,  14,  235.) 

Method  II. — 50  c.cs.  (excess)  of  a  saturated  solution  of  sodium  bisulphite 
are  added  to  15  gms.  (1  mol.)  of  freshly  distilled  benzaldehyde  in  a  beaker, 
and  the  whole  stirred  until  the  mass  is  semi-solid  owing  to  the  separation 
of  the  bisulphite  compound  of  the  aldehyde.  The  latter  is  filtered  off  at 
the  pump,  pressed,  and  washed  with  a  little  water  and  alcohol.  It  is  then 
stirred  up  with  water  to  a  thick  paste,  and  a  30%  solution  of  12  gms. 


152  SYSTEMATIC  ORGANIC  CHEMISTRY 


(excess)  of  potassium  cyanide  is  added.  After  stirring  for  a  short  time, 
the  crystals  go  into  solution  and  the  nitrile  appears  as  an  oil,  which  is 
separated  and  washed  with  water  as  above. 

C6H5CHO  +  NaHS03  =  C6H5CH(OH)O.S02Na. 
C6H5CH(OH)O.S02Na  +  KCN  =  C6H5CH(OH)CN  +  K.Na.S03. 

Yield. — Theoretical  (20  gms.).  Reddish  unstable  oil ;  decomposes  on 
heating.    (B.,  39,  1224  ;  D.R.P.,  85230  ;  C.  Z.,  (1896),  90.) 

Reaction  L.  (6)  Condensation  of  an  Aldehyde  with  Ammonia  and 
Hydrogen  Cyanide  (Strecker-Tiemann-Bucherer-Knoevenagel).  (A.,  75, 
27  ;  94,  234  ;  176,  341  ;  211,  359  ;  B.,  13,  381  ;  33,  2372  ;  39,  989,  1722, 
2796,  4059,  4073,  4087.)— When  an  aldehyde-ammonia  is  treated  with 
hydrogen  cyanide,  an  amino-nitrile  is  formed  (A.,  75,  27,  94,  243  ;  176, 
341,  211,  359  ;  B.,  33,  2372  ;  37,  1809). 

R.CH(OH)NH2  +  HCN  =  KCH(CN)NH2  +  H20. 

The  two  steps  in  this  synthesis  are  interchangeable  (B.,  13,  381). 

R.CH(CN)OH  +  NH3  =  RCH(CN)NH2  +  H20. 

The  use  of  the  cone,  hydrocyanic  acid  necessary  in  the  above  reactions 
can  be  avoided,  and  the  amino-nitrile  synthesised  in  one  stage  by  using 
ammonium  cyanide  or  an  equimolecular  mixture  of  ammonium  chloride 
and  potassium  cyanide  ;  this  also  brings  ketones  within  the  scope  of  the 
reaction  (B.,  39,  1722).  The  condensation  is  carried  out  in  aqueous  or 
aqueous  alcoholic  solutions.  An  extension  of  this  reaction  permits  the 
use  of  primary  aromatic  amines  and  potassium  cyanide  in  place  of  am- 
monium chloride  and  potassium  cyanide  (D.P.R.,  157710 ;  157709  ; 
158090,  158346  ;  B.,  37,  4059,  4073,  4087  ;  39,  989,  2796). 

Better  results  are  here  obtained  by  using  the  bisulphite  compound  of  the 
aldehyde  or  ketone  (cf.  Reaction  L.  (a)  ). 

ArNH2  +  KCN 

RRiCO  ->  RR1C(OH)S03Na  —  >  RR1C(CN)(NHAr). 

In  the  following  preparation,  the  amino-nitrile  formed  is  hydrolysed 
directly  to  the  corresponding  amino-acid.  These  latter  are  of  great 
importance  in  the  chemistry  of  the  proteins. 

Preparation  84.  —  Racemic  Leucine  (Racemic-4-methyl-2-amino- 
pentan  acid). 

(CH3)2.CH.CH2.CH(NH2).COOH.       C6H1302N.  131. 

(This  preparation  must  he  carried  out  in  a  good  fume  cupboard.) 

50  gms.  (1  mol.)  of  pure  redistilled  iso- valeric-aldehyde  are  dissolved  in 
100  c.cs.  of  absolute  ether  (see  p.  209)  and  the  solution  cooled  in  ice  and 
saturated  with  dry  ammonia  (see  p.  503).  The  water  formed  in  the 
reaction  is  separated  by  means  of  a  funnel,  the  ethereal  solution  is  shaken 
with  a  little  potassium  carbonate,  filtered,  and  evaporated  under  reduced 
pressure  at  a  temperature  not  greater  than  25°.  The  oily  residue  of  iso- 
valeraldehyde-ammonia  which  usually  crystallises  rapidly,  is  at  once 


CARBON  TO  CARBON 


153 


suspended  in  100  c.cs.  of  water  ;  the  liquid  is  cooled,  and  36  c.cs.  (1  mol. 
HON)  of  50%  hydrocyanic  acid  are  gradually  added  (caution!).  The 
mixture  is  allowed  to  stand,  with  frequent  shaking  for  12  hours,  and  then 
a  mixture  of  400  c.cs.  (excess)  of  cone,  hydrochloric  acid  (D.  1-19)  and 
200  c.cs.  of  water  is  added.  This  produces  a  lumpy  precipitate,  which  is 
dissolved  by  prolonged  boiling  in  a  flask  ;  another  200  c.cs.  of  water  are 
added,  and  the  boiling  continued  for  2  hours  more.  The  mixture  is 
finally  evaporated  to  dryness  on  a  water  bath  to  remove  hydrochloric 
acid.  The  residue  is  warmed  with  about  60  c.cs.  of  water  and  made  faintly 
alkaline  with  ammonia.  When  cold,  the  leucine  which  has  separated  is 
filtered  off  at  the  pump  and  washed  with  cold  water  until  all  the  am- 
monium chloride  has  been  removed.  Further  purification  is  effected  by 
recrystallising  from  hot  water  with  the  addition  of  animal  charcoal.  The 
mother  liquor  is  concentrated  or  treated  with  absolute  alcohol  to  obtain 
any  leucine  remaining  dissolved  therein. 

(CH3)2:  CH  .  CH2.CHO  +  NH3  =  (CH3)2.CH  :  CH2.CH(OH)NH2 
(CH3)9  :  CH.CH2CH(OH)(NH2)  +  HCN  =  (CH3)2  :  CH.CH2.CH(CN)(NH2) 

+  H20. 

H20 

(CH3)2:  CH.CH2.CH(CN)(NH2)  >  (CH0)2  :  CH.CH2CH.(NH2)COOH. 

Yield.— 33%  theoretical  (25  gms.).  Shining  leaflets  ;  slightly  soluble 
in  cold  water  ;  very  slightly  in  hot  alcohol ;  decomposes  on  heating. 
(A.,  94,  243  ;  316,  145  ;  B.,  33,  2372.) 

Preparation  85 . — o-Carboxy-phenamino-acetonitrile  (1-  (cyanmethyl- 
amino)-2-carboxy-benzene). 

C6H4.(NH.CH2CN)(COOH)[l  :  2].       C9H802N2.  176. 

Method  I. — 7  gms.  (1  mol.)  of  finely  powdered  potassium  cyanide  and 
14  gms.  (1  mol.)  of  finely  powdered  anthranilic  acid  are  suspended  in 
50  c.cs.  of  ether  or  benzene  in  a  flask  fitted  with  a  reflux  condenser.  The 
whole  is  well  cooled  in  a  freezing  mixture,  and  7-5  c.cs.  (1  mol.  CH20)  of 
40%  formalin  are  slowly  added.  A  brisk  reaction  sets  in,  and  two  layers 
are  formed,  the  lower  of  which  solidifies  on  cooling  to  a  mass  of  crystals  of 
the  potassium  salt  of  the  required  acid.  This  is  collected,  dissolved  in 
water,  the  free  acid  precipitated  by  acidification  with  acetic  or  hydro- 
chloric acids,  washed  with  cold  water,  and  recrystallised  from  alcohol, 
benzene,  or  chloroform. 

CH20 

C6H4(NH2)(COOH)[l  :  2]   ►  CH2(OH).NHC6H4.COOH[l  :  2] 

K.CN  HC1 

 >  CH2(CN).NH.C6H4COOK[l  :  2]  — >  CH2(CN)NH.C6H4COOH[l  :  2]. 

Yield. — Theoretical  (18  gms.). 

Method  II. — 20  c.cs.  (1  mol.  NaHS03)  of  40%  sodium  bisulphite  solution, 
and  7-5  c.cs.  (1  mol.  CH20)  of  40%  formalin  are  mixed,  and  the  mixture 
kept  at  60° — 70°  for  about  20.  minutes  until  the  smell  of  formaldehyde  has 
vanished.  A  solution  of  14  gms.  (1  mol.)  of  anthranilic  acid  in  10-3  c.cs. 
(exactly  1  mol.  NaOH)  of  30%  caustic  soda  solution  is  then  added,  and  the 
whole  heated  on  a  water  bath  until  no  more  anthranilic  acid  is  present 


154  SYSTEMATIC  ORGANIC  CHEMISTRY 


(about  45  minutes).  To  test  the  reaction  mixture,  a  sample  is  withdrawn 
at  intervals,  acidified  with  an  excess  of  acetic  acid,  a  few  drops  of  sodium 
nitrite  added  to  the  well-cooled  mixture,  and  the  whole  poured  into  an 
alkaline  solution  of  R-salt.  Anthranilic  acid  is  absent  when  no  red  azo- 
colour  is  obtained.  When  the  test  is  negative,  or  nearly  so,  a  solution  of 
7  gms.  (1  mol.)  of  potassium  cyanide  in  25  c.cs.  of  water  is  added,  and  the 
whole  heated  to  7 0° — 80°  for  20  minutes.  On  cooling,  an  excess  of  glacial 
acetic  acid  is  added,  and  the  nitrile  filtered  off  and  purified  as  before. 

CH2(OH)(S03Na) 

C6H4(NH2)(COONa)[l:2]  >  CH2(S03Na)NH.C6H4COONa[l:2] 

KCN  CH3COOH 

— »CH2(CN)NH.C6H4COONa[l:2]  >CH2(CN)NH.C6H4COOH[l:2] 

Yield. — Theoretical  (18  gms.).  Crystallises  from  alcohol  (3  parts)  in 
leaflets  ;  from  benzene  or  chloroform  in  long  needles  ;  insoluble  in  water  ; 
M.P.  183°.    (D.R.P.,  157909  ;  B.,  39,  2807.) 

Reaction  L.  (c)  Action  of  Hydrogen  Cyanide  on  Quinones.  (B.,  33, 
675  ;  D.R.P.,  117005.) — Hydrogen  cyanide  reacts  easily  with  quinones 
to  give  di-cyan-di-hydroxy  derivatives  of  the  parent  hydrocarbons.  A 
molecule  of  the  quinone  is  simultaneously  reduced. 

O  OH 


I! 

O 
O 


2HCN  = 


-CN 


EL 


-CN 


OH 
OH 


0 


Yh 


Preparation  86.  — 
benzene). 

OH 

/\CN 

CN 
OH 


Dicyanoquinol  (1:4-  Dihydroxy  -2:3-  dicyano- 


C8H402N. 


160. 


(This  preparation  must  be  carried  out  in  a  fume  cupboard.) 

20  gms.  (2  mols.)  of  ^-benzoquinone  are  dissolved  in  60  c.cs.  of  alcohol, 


CARBON  TO  CARBON 


155 


and  a  cold  mixture  of  25  c.cs.  (excess)  of  cone,  sulphuric  acid  and  50  c.cs.  of 
alcohol  are  added.  The  mixture  is  well  cooled  in  a  freezing  mixture,  and 
a  50%  solution  of  potassium  cyanide  (caution  !)  slowly  run  in  until  a 
green  fluorescence  appears,  and  the  liquid  reacts  alkaline.  About  110  gms. 
of  solution  will  be  required.  The  whole  is  then  acidified  with  sulphuric 
acid  (caution !)  and  the  alcohol  removed  by  distillation  under  reduced 
pressure  from  a  water  bath.  The  residue  is  washed  with  water,  and 
recrystallised  from  hot  water  with  the  addition  of  animal  charcoal. 

2C6H402  +  2HCN  =  C6H(OH)2(CN)2[l  :  4  :  2  :  3]  +  C6H4(OH)2[l  :  4]. 

Crystallises  in  pale  yellow  leaflets,  which  contain  2  mols.  of  water  ; 
slightly  soluble  in  water  ;  its  neutral  solution  fluoresces  blue,  its  acid 
solution  violet,  and  its  alkaline  solution  green  ;  on  heating  it  decolorises 
at  230°.    (B.,  33,  675  ;  D.P.R.,  117005.) 

Reaction  LI.  (a)  Action  of  Acids  on  the  non-para  substituted  Hydrazo 
Compounds.  (A.,  270,  330  ;  287,  97  ;  B.,  26,  681,  688,  699.)— When 
hydrazobenzene  is  treated  with  mineral  acids,  an  intermolecular  rearrange- 
ment to  benzidine  (^-jOg-diaminodiphenyl)  takes  place. 

C6H5.NH.NH.C6H5  ->  H2N.C6H4.C6H4NH2[4  :  4'.] 

This  reaction  can  be  extended  to  almost  all  non-para  substituted 
hydrazo  compounds  ;  if  one  or  both  joara-positions  are  substituted,  either 
or^o-benzidine  or  diphenylamine  derivatives  known  as  ortho-  or  para- 
semidines  are  formed. 


NH  NH< 


NH2/  NH2 

•NH-A       (  V- NH— 


o-Benzidine.  o-Semidine.  ^>-Semidine. 


NH. 


Benzidine  and  its  homologues  are  very  important  intermediates  in  the 
dye  industry. 

Preparation  87. — Benzidine  (4  :  4'-Diamino-l :  l'-di-phenyl). 


H2N./  ^>  <^  )NH2.       C12H12N2.  184. 

5  gms.  (1  mol.)  of  hydrazobenzene  are  shaken  with  20  c.cs.  of  cone,  hydro- 
chloric acid  for  10  minutes.  The  diluted  solution  is  made  alkaline  with 
caustic  soda,  extracted  several  times  with  ether,  and  the  latter  removed 
on  a  water  bath.  The  benzidine  which  remains  is  washed  with  cold 
water,  and  recrystallised  from  boiling  water. 

C6H8NH.NH.C6H5  ->  H2N.C6H4C6H4NH2[4  :  4']. 

Yield. — Almost  theoretical  (5  gms.).    Lustrous  plates  when  freshly 


156  SYSTEMATIC  ORGANIC  CHEMISTRY 


crystallised  ;  darkens  in  air  ;  soluble  in  hot  water  ;  M.P.  127°  ;  forms  a 
difficultly  soluble  sulphate.    (J.  pr.,  [1],  36,  93.) 
Reaction  LI.    (b)  Molecular  rearrangement  of  Di-benzanilides.— When 

dibenzanilide  is  heated  to  230°  for  2  days,  rearrangement  takes  place,  and 
2  and  4-(benzoylamino)-benzophenones  are  formed. 

NH(COC6H5)  NH(COC6H5) 
/\  /^COC6H5 
C6H5N(COC6H5)2  >  and 


COC6H5 

If  either  the  o-  or  ^-position  is  occupied,  only  one  isomer  is  obtained  ; 
transformation  to  the  meto-position  does  not  occur.  This  is  a  standard 
method  of  preparation  of  acyl-amino-ketones,  or  by  a  further  hydrolysis, 
of  aminoketones.  The  tendency,  illustrated  in  this  reaction,  of  groups  to 
wander  from  the  amino  group  to  the  nucleus,  is  also  shown  in  previous 
reactions  and  in  the  preparation  of  amino-azobenzene  from  diazoamino- 
benzene  (Preparation  456)  of  sulphanilic  acid  from  aniline  sulphate  (Pre- 
paration 290)  of  o-  and  ^-chloracetanilides  from  acetchloranilide  (Pre- 
paration 327)  of  o-  and  j9-toluidine  from  methylaniline  hydrochloride,  and 
of  1  :  2  :  4-aminodimethylbenzene  (2  :  4-xyhdine)  from  dimethylaniline 
hydrochloride. 

Preparation  88.  —  4-Amino-3-methyl  benzophenone  (l-Methyl-2- 
benzoyl-6-amino  benzene). 


NH, 


CH. 


COC6H5. 


211. 


To  26  gms.  (2  mols.)  of  benzoyl  chloride  are  added  gradually  10  gms.  of 
o-toluidine  (1  mol.)  and  the  mixture  is  heated  for  15  hours  in  an  oil  bath 
at  230°.  A  brown  viscid  liquid  is  formed  which  solidifies  on  cooling.  In 
order  easily  to  separate  the  4-amino  3-methyl  benzophenone,  the  mass  is 
hydrolysed  by  boiling  for  14  hours  with  excess  of  alcohol  containing  half 
its  bulk  of  cone,  hydrochloric  acid.  The  product  thus  obtained  is  steam- 
distilled  when  alcohol  and  then  ethyl  benzoate  pass  over.  The  acid 
residue  which  contains  the  hydrochloride  of  the  base  is  boiled  for  some 
time  with  water  and  filtered  from  tarry  matter.  The  filtrate  is  then  made 
slightly  alkaline,  and  o-toluidine  derived  from  untransformed  dibenzoyl- 
o-toluidine,  removed  by  steam  distillation.  A  solid  separates  from  the 
alkaline  liquid  in  the  flask,  and  after  cooling  this  is  filtered  off  and  ex- 
tracted with  absolute  alcohol.  The  alcohol  is  almost  completely  removed 
on  the  water  bath,  and  a  few  drops  of  cone,  sulphuric  acid  are  added.  On 
adding  a  little  ether,  the  base  crystallises  out  in  the  form  of  colourless 
needles. 


CARBON  TO  CARBON 


157 


CH3.C6H4.NH2[1.2]  +  2C6HBC0C1  ->  CH3C6H, .N(COC6H,)2  +  2HC1 
CH3  C6H4N(COC6H5)2  ->  CH3.C6H3(COC6H5)NH(COC6H5)  [1.5.2J 
HC1  +  C2H5OH 

 >    CH3.C6H3.(COC6H5)NH2.HCl  +  C6H5COOC2H5 

NaOH 

 >    CH3.C6H3.(COC6H5)NH2  [1.5.2]. 

Colourless  needles  ;  soluble  in  alcohol ;  insoluble  in  ether  and  in  water. 
(J.  C.  S.,  85,  386,  591.) 

Reaction  LII.  (a)  Action  of  Copper  Powder  on  2-  and  4-mono-nitro- 
and  2 : 4-di-nitro-chloro-  and  bromo-benzenes  and  their  Homologues. 

(B.,  34,  2172.) — Symmetrical  diphenyl  derivatives  can  be  prepared  by 
heating  aromatic  iodo-compounds  with  copper  powder  (see  Reaction 
VII.  (b) ).  Chloro-  and  bromo-compounds,  however,  only  react  when 
activated  by  nitro  groups  in  the  ortho-  or  ^am-positions.  Di-nitro-di- 
phenyl  derivatives  can  be  obtained  from  them  in  good  yield  by  heating 
with  the  metallic  powder  to  about  250°  in  sealed  tubes.  If  both  the  ortho- 
and  ^ara-positions  are  occupied  by  nitro  groups,  the  activation  of  the 
halogen  atom  is  such  that  the  corresponding  diphenyl  derivative  can  be 
prepared  by  boiling  with  copper  powder  in  nitrobenzene  solution. 

N02  .  N02  NQ2 


>C1  +  2Cu 


+  Cu2CL 


Preparation  89.  —  o-^-o '-^'-Tetranitro-diphenyl  (l-(2' :  4'-Dinitro- 
phenyl)-2  : 4-dinitrobenzene). 

[2.4](N02)2C6H3.C6H3(N02)2[2'.4'.J.       C12H608N4.  334. 

10  gms.  (1  mol.)  of  2-4-dinitrochlorbenzene  (see  p.  266),  10  gms. 
(excess)  of  copper  powder,  and  20  c.cs.  of  nitrobenzene  are  refmxed  for  1 
hour  and  the  cooled  solution  diluted  with  ether  and  filtered.  Ligroin  is 
slowly  added  to  the  filtrate  and  the  oil  which  separates  crystallised  by 
scratching  the  sides  of  the  vessel.    It  is  recrystallised  from  benzene. 

[1:2:  4](N02)2C6H3C1  +  2Cu  +  C1C6H3(N02)2[  1  :  2  :  4.]  = 
[2.4](NOa)aC.eH8.C6H,(N02)S![2/.4']  +  Cu2Cl2. 

Yield. — 66%  theoretical  (5-5  gms.).  Yellowish  prisms  ;  insoluble  in 
petroleum  ether  ;  M.P.  163°.    (B.,  34,  2177.) 

Reaction  LII.  (6)  Action  of  Cuprous  Chloride  on  Nitro-diazonium  Com- 
pounds. (B.,  34,  3802  ;  38,  725.) — Ordinarily  when  cuprous  chloride  acts 
on  a  diazonium  salt  in  acid  solution,  a  chloro-compound  is  the  chief  pro- 
duct (Sandmeyers  reaction,  p.  338),  and  only  a  small  quantity  of  the 
corresponding  diphenyl  compound  is  formed.  But  if  a  nitro-diazonium 
salt  be  used,  the  diphenyl  derivative  is  formed  in  much  larger  quantities. 
The  same  holds  good  for  Gattermann's  modification  of  the  reaction  using 
copper  powder  (B.,  23,  1226). 

2C6H4(N02)N2C1  +  Cu2Cl2  =  (N02)C6H4.C6H4(N02)  +  2CuCl2  +  2N2. 


158  SYSTEMATIC  ORGANIC  CHEMISTRY 


Peeparation  90.— p-p  '-Dinitrodiphenyl  (l-(4-Nitro-phenyl)-4-nitro- 
benzene). 


NO/  >  <  >N02.       C12H8N204.  244. 


By-product  ^-Chloro-nitro-benzene.  (l-Chloro-4-nitro -benzene) 
C6H4(C1)(N02)[1  :  4.]       C6H402NC1.  157-5. 

A  cold  solution  of  21-6  gms.  (1  mol.)  of  cuprous  chloride  in  100  c.cs.  of 
cone,  hydrochloric  acid  (see  p.  502)  is  added  to  the  diazo  solution 
prepared  from  30  gms.  (1  mol.)  of  j9-nitraniline,  45  gms.  (excess)  of 
cone,  sulphuric  acid,  60  c.cs.  of  water  and  15-3  gms.  (1  mol.)  of  sodium 
nitrite. 

During  the  addition  of  the  copper  salt  the  whole  is  vigorously  stirred. 
There  is  a  brisk  evolution  of  nitrogen,  the  mass  turns  black  and  a  brownish- 
yellow  substance  is  precipitated.  When  the  liquid  becomes  green,  the 
reaction  is  finished.  The  product  is  distilled  in  steam  until  no  more 
p-chloro-nitro-benzene  passes  over.  There  remains  in  the  distilling 
flask  almost  pure  4  :  4'-di-nitro-diphenyl.  It  is  filtered  off,  dried,  and 
recrystallised  from  benzene.  The  by-product  £>-chloronitrobenzene  is 
worked  up  by  filtering  it  from  the  liquid  portion  of  the  distillate,  drying 
on  a  porous  plate,  and  recrystallising  from  benzene. 


HNO. 


%  N02C  >N2C1. 


--^  NO  /  \-  >N02 


and        NO,<  >C1. 


Yield. — 4  :  4' ' -dinitrophenyl  55%  theoretical  (14  gms.) ;  p-chloronitro- 
benzene  40%  theoretical  (13  gms.).  4  :  4' -dinitrodiphenyl  is  a  crystalline 
solid  ;  M.P.  237°  ;  p-chloronitrobenzene  is  a  crystalline  solid  ;  M.P.  83°  ; 
B.P.  238-5°.    (B.,  38,  726.) 

In  an  exactly  analogous  manner  there  is  obtained  from  30  gms.  of 
m-nitraniline,  23  gms.  (87%)  of  3-3 '-dinitrodiphenyl  (yellow  needles  ; 
insoluble  in  cold  glacial  acetic  acid  ;  M.P.  200°)  and  6  gms.  (20%)  of 
m-chloronitrobenzene  ;  (colourless  crystals  ;  insoluble  in  cold  benzene  ; 
M.P.  45°  ;  if  rapidly  cooled  after  fusion,  melts  at  24°,  but  in  a  short  time 
reverts  to  the  stable  modification). 

Similarly  30  gms.  of  o-nitraniline  yield  17-6  gms.  (64%)  of  2  :  2'-di- 
nitro-diphenyl  (crystalline  solid,  insoluble  in  cold  benzene  ;  M.P.  127°) 
and  9  gms.  (30%)  of  o-nitrochloro-benzene  (colourless  crystals,  insoluble 
in  cold  benzene  ;  M.P.  32-5°). 

Reaction  LIII.  Action  of  Aceto-acetic  Ester  on  Aldehyde-ammonias 
(Hantzsch).  (A.,  215,  1.) — When  aceto-acetic  ester  is  heated  with 
aldehyde  ammonias  alkyl  derivatives  of  dimethyl-dihydro-pyridine-di- 
carboxylic  ester  are  produced. 


! 


CARBON  TO  CARBON 


159 


R  R 

I  I 
OCH  CH 
C6H5O.OC.CH2    CH2.CO.C2H5  /\ 

|         |  ->     C2H5O.OCC  C.CO.OC2H5 

CH3CO     CO.CH3  |l  || 

CH3— C    C— CH3 
HNH2  \/ 

N        +  3H20 
1 

H 

A  great  many  aldehydes  can  be  employed — propionic  aldehyde,  nitro- 
benzaldehyde,  phenylacetaldehyde,  furfurol — so  that  the  reaction  is  of 
wide  application.  For  the  steps  in  the  conversion  of  the  compounds 
obtained  to  alkyl  or  aryl  derivatives  of  di-methyl-pyridine,  see  pp.  235, 
403,404. 

Preparation  91.  —  Diethyl-dihydro-collidine-dicarboxylate  (2:4:6- 
Trimethyl-3  : 5  dicarbethoxyl-piperidine-(2)-(5)-di-en). 

CH3 
CH 

C2H5OOC.C./\C.COOC2H5.       C14H2104N.  267. 

II  li 
CH3.C\/C.CH3 
NH 

13  gms.  (slightly  more  than  1  mol.)  of  acetaldehy de-ammonia  (see 
p.  300)  are  covered  with  80  gms.  (2  mols.)  of  ethyl  aceto-acetate  and 
warmed  gently  (in  a  fume  cupboard)  until  ebullition  has  commenced 
(100° — 110°,  stir  with  a  thermometer).  Should  the  reaction  become  too 
violent,  the  heating  is  stopped  until  it  subsides.  In  5  minutes  the  reaction 
is  completed,  and  an  equal  volume  of  dilute  hydrochloric  acid  is  added 
with  stirring  to  the  hot  liquid,  the  stirring  being  continued  until  the  oil 
which  separates  sets  to  a  white  crystalline  mass.  This  latter  is  powdered, 
filtered,  washed  first  with  diluted  hydrochloric  acid,  and  then  with  water, 
well  pressed  and  recrystallised  from  the  minimum  quantity  of  hot  alcohol. 

CH3 

I  CH3 
0  :  CH  CH 


\  ->   EtOOC.C/  \C.COOEt. 

H3C.CO  0  :  C.CH3  _j_  3jj2Q 

H.N.H  H3C.C\v/C.CH3 
H  NH 

Yield. — 60%  theoretical  (30  gms.).  Colourless  plates  with  bluish 
fluorescence  ;  insoluble  in  water  ;  sparingly  soluble  in  alcohol  ether  and 
carbon  disulphide  ;  readily  soluble  in  benzene  ;  M.P.  131°.    (A.,  215,  1.) 

Reaction  LIV.  (a)  Condensation  of  Non-di-ortho-substituted-primary- 
aromatic  Amines  with  Acrolein  (Skraup).  (M.,  1,  316  ;  2, 141  ;  B.,  13,  911  ; 


160  SYSTEMATIC  ORGANIC  CHEMISTEY 


14,  1002  ;  29,  705.) — When  a  primary  aromatic  amine  which  has  a  non- 
substituted  carbon  in  the  or^o-position  is  heated  with  glycerol  and  cone, 
sulphuric  acid  in  the  presence  of  an  oxidising  agent,  the  following  series  of 
reactions  occur  : — 

(i.)  The  glycerol  is  dehydrated  by  the  acid  to  acrolein. 

-2H20 

CH2OH.CHOH.CH2OH  >  CH2  =  CH.CHO. 

(ii.)  The  aldehyde  then  condenses  with  the  aromatic  amine  to  form 
an  aldehyde-amine. 

CH2 :  CH.CHO  +  KNH2  ->  CH2 :  CH.CH  :  N.K  +  H20. 

(iii.)  The  latter  compound  under  the  influence  of  the  oxidising  agent 
condenses  to  a  derivative  of  quinoline. 

CH 

/\  /\/\CH 
0  I 

I  |CH 

\y  x/\/ 

N  :  CH.CH  :  CH2  N 

The  oxidising  agent  usually  employed  is  the  nitro-compound  corre- 
sponding to  the  amine,  e.g.,  nitro-benzene  when  aniline  is  the  base  ;  for 
2?-toluidine,  ^-nitro-toluene  serves,  and  so  on.  Arsenic  acid,  however, 
can  be  generally  employed,  and  gives  better  results.  The  reaction  is 
capable  of  very  wide  application  ;  nitro-,  halogen-,  hydroxy-,  carboxy- 
quinolines  can  all  be  obtained  from  the  corresponding  amines  ;  the 
amino-naphthalenes  also  react.  Diamines  yield  the  so-called  phen- 
anthrolines.    (B.,  16,  2519  ;  23,  1016.) 


h2n/\/\nh2 

N 


m-Phenanthroline. 


Sometimes  the  amine  can  be  dispensed  with,  and  the  corresponding 
nitro-body  used  alone.  It  is  reduced  by  the  hydrogen  arising  in  the 
reaction.  Of  technical  interest  is  the  fact  that  ^-nitro-alizarin  on 
heating  with  glycerol  and  sulphuric  acid  yields  a  blue  dye — Alizarin  Blue. 
(B.,  16,  445  ;  29,  708  ;  A.,  201,  333.) 


OH  OH 

CO  CO  | 

-OH  /\/\/\.  -OH 


CO  CO 

Alizarin  Blue. 


CARBON  TO  CARBON 


161 


Preparation  92. — Quinoline  (Benz-pyridine). 

C9H7N.  129. 


N 


125  gms.  of  cone,  sulphuric  acid  are  gradually  added,  with  shaking  to  a 
mixture  of  46  gms.  (1  mol.)  of  aniline,  30  gms.  of  nitrobenzene  and  125  gms. 
(excess)  of  glycerol  contained  in  a  2-litre  round-bottomed  flask.  The 
latter  is  fitted  with  a  long  wide  reflux  condenser,  and  heated  on  a  sand 
bath  until  bubbles  of  white  vapour  are  evolved.  The  source  of  heat  is 
removed  until  the  reaction  moderates,  when  the  flask  is  again  heated  to 
gentle  ebullition  for  3  hours.  Water  is  added,  and  the  unchanged  nitro- 
benzene distilled  off  in  steam.  The  residue  is  treated  with  cone,  caustic 
soda  solution  until  it  is  strongly  alkaline,  and  the  quinoline  and  aniline 
present  distilled  off  in  steam.  The  distillate  is  treated  with  dilute  sul- 
phuric acid  until  the  bases  are  both  completely  dissolved  and  the  solution 
contains  excess  of  acid.  To  the  cooled  solution  sodium  nitrite  solution  is 
added  until  a  drop  of  the  solution  gives  a  blue  coloration  with  potassium- 
iodide-starch  paper  (see  p.  501).  The  aniline  is  thus  converted  into 
the  diazonium  compound,  and  on  boiling  on  a  water  bath,  the  latter 
passes  into  phenol.  The  solution  is  again  made  alkaline,  and  the 
quinoline  distilled  off  in  steam.  The  distillate  is  extracted  with  ether, 
dehydrated  over  solid  caustic  potash,  the  ether  removed  on  a  water 
bath,  and  the  residue  distilled. 


CH2 
H  \CH 

JCH  ^   


+  H20 


Yield. — 70%  theoretical  (45  gms.).  Colourless  liquid  ;  characteristic 
odour  ;  insoluble  in  water  ;  soluble  in  alcohol  and  ether  ;  B.P.  237°  ; 
D.  I  1-108.    (B.,  13,  911  ;  14,  1002.) 

Preparation  93. — o-Nitroquinoline  (o-nitro-benzpyridine). 


C9H602N2.  174. 


100  gms.  of  cone,  sulphuric  acid  and  51-5  gms.  of  arsenic  acid  are  well 
shaken  in  a  flask  with  110  gms.  glycerine  and  50  gms.  of  o-nitraniline — and 
then  carefully  heated  on  a  sand  bath  under  a  reflux  condenser.  As  soon 
as  the  reaction  begins,  the  flask  is  removed  from  the  sand  bath  until  it 
has  moderated  ;  it  is  then  boiled  for  3  hours.  When  cold,  a  large  volume 
of  water  is  added  to  the  contents  of  the  flask,  and  the  whole  allowed  to 
stand  overnight,  and  then  filtered.    Caustic  soda  is  carefully  added  to  the 

s.o.c.  M 


162  SYSTEMATIC  ORGANIC  CHEMISTRY 


filtrate  until  a  brown  precipitate  appears,  which  is  filtered  off  and  dis- 
carded. Caustic  soda  is  then  added  to  the  filtrate  until  alkaline.  The 
nitro-quinoline  thus  obtained  is  washed  with  water,  boiled  up  with 
alcohol  and  animal  charcoal,  and  after  filtration  is  precipitated  by  the 
addition  of  water. 


O  :  CH2 

/\h  \ch 


CH 


+  H20 


NO,  N 


Yield. — 55%  theoretical  (35  gms.).  Colourless  monoclinic  needles  ; 
insoluble  in  water  ;  soluble  in  alcohol ;  M.P.  88°.    (B.,  29,  705.) 

Reaction  LIV.  (b)  Condensation  of  Primary  Aromatic  Amines,  other 
than  Ortho  Substituted,  with  two  Molecules  of  certain  Aldehydes  (containing 
the  group  — CH2CHO)  under  the  influence  of  Sulphuric  or  Hydrochloric 
Acid.  (B.,  16,  2415  ;  A.,  249, 110.) — Quinolines  substituted  in  the  benzene 
or  in  both  nuclei  may  be  formed,  an  intermediate  stage  being  an  aldehyde- 
amine. 

RiNH2  +  OHC.CH2.E  ->  RXN  :  CH.CH2E. 

Two  molecules  of  the  latter  then  condense  to 

RjN  =  CHCHE 

I 

EjNH.CH 

CH2E 

which  splits  off  amine  and  hydrogen  to  give  a  quinoline  derivative  (B., 
29,  59). 

(Ri-H) 

\n 

[2] 


-CH  =  CE 

I 

CCH9E. 


That  hydrogen  is  set  free  is  proved  by  the  reduction  of;  some  of  the 
quinoline  derivative  to  a  tetrahydroquinoline  derivative.  A  mixture  of 
two  aldehydes,  or  of  an  aldehyde  and  a  ketone,  may  be  employed.  (B.,  20, 
1908.) 

An  alkylidene-aniline  may  be  substituted  for  the  primary  amine,  and 
the  condensation  takes  place  in  presence  of  zinc  chloride. 


C6H5N  :  CHCH3  +  CH3CHO 


CARBON  TO  CARBON 


ir>3 


Peeparation  94. — Quinaldine  (a-Methyl-quinoline). 

C10H9N.  143. 


To  a  mixture  of  30  gms.  cone,  hydrochloric  acid  and  10  gms.  zinc 
chloride  are  added  15  gms.  (1  mol.)  of  aniline,  and  the  whole  is  remixed  on 
a  water  bath.  To  this  is  slowly  added  during  2  hours,  12|  gms.  (2  mols.) 
of  acetaldehyde.  The  whole  is  boiled  on  a  sand  bath  for  90  minutes,  and 
after  making  alkaline  with  caustic  soda,  is  steam-distilled.  The  quin- 
aldine is  separated  and  distilled,  the  fraction  244°— 250°  being  collected. 

CH 
/  CH 

2C2H5NH2  +  2CH3CHO  ->  2C6H5N  :  CHCH3  — >  C6H4  j 

XN=C.CH3. 

Yield. — 50%  theoretical  (10  gms.).  Colourless  liquid  ;  characteristic 
odour  ;  insoluble  in  water  ;  B.P.  247°.    (B.,  16,  2465  ;  D.R.P.,  28217.) 

Reaction  LIV.  (c)  Condensation  of  o-Amino-benzaldehydes  with  Alde- 
hydes, Ketones,  Aceto-acetic  Ester,  etc.  under  the  influence  of  a  trace  of 
Sodium  Hydroxide,  to  give  Quinoline  Derivatives  (B.,  16,  1835 ;  25, 1752.) — 
The  first  stage  is  the  formation  of  an  o-amino-benzo  ketone. 

CH 

!NH2        +     CH3COCH3  - >      I     lNBi2  I 

CO.CH3, 

which,  like  all  such  compounds,  readily  condenses  to  quinoline  derivatives. 
CH  =  CH  CH=CH 

C«H<       !   >     cqr{  I 

NH2  OC.CH3  \  I 

N  C.CII3. 

The  reaction  usually  takes  place  by  gentle  warming  with  a  trace  of 
alkali  in  alcoholic  solution.  Prolonged  heating  at  150°  is  necessary, 
however,  and  alcohol  and  alkali  are  no  longer  employed  in  the 
condensation  to  y-hydroxyquinolines  of  the  anthranilic  acids  and 
aldehydes,  ketones,  etc.  (B.,  28,  2809.) 

An  interesting  synthesis  of  quinoline  from  o-toluidine  is  given  by  con 
densation  with  glyoxal  (B.,  27,  628). 


CH3  O.CH  /x  /CH  /v  yCH 

CH   > 


NH2         O.CH  V\Nh2  OCH 

(Cf.  the  synthesis  of  Carbostryl,  B.,  14,  1916). 


CH 

I 


N 

M  2 


164  SYSTEMATIC  ORGANIC  CHEMISTRY 


Pkepaeation  95. — Quinaldine  (a-Methyl-quinoline), 


C10H9N.  143. 


\/\/CH3 
N 


20  gms.  (1  mol.)  of  o-amino-benzaldehyde  and  9  gms.  (1  mol.)  of  dried 
and  redistilled  acetone  are  dissolved  in  absolute  alcohol,  and  a  few  drops  of 
alcoholic  caustic  soda  added.  The  condensation  takes  place  at  the 
ordinary  temperature.  The  quinaldine  is  distilled  off  in  steam  and  washed 
with  water  until  free  from  acetone. 


H2CH 


CH 


\/\NH2 


0  :  C.CIL 


Yield. — Theoretical  (23  gms.).  Colourless  liquid  ;  insoluble  in  water  ; 
B.P.  247°.    (B.,  16,  1834.) 

Reaction  LV.  Intramolecular  condensation  of  Phenyl  Hydrazones  of 
Aldehydes,  Ketones  and  Ketonic  Acids  by  heating  with  Hydrochloric  Acid  or 
Zinc  Chloride  (Fischer).  (B.,  19,  1563  ;  26,  R.,  14.)— This  is  an  important 
preparation-method  for  the  alkylindols.  The  reactions  occurring  are 
somewhat  complicated,  since  both  a  rearrangement  and  a  splitting  off  of 
ammonia  takes  place. 

rs- — CH, 


C6H5NH.N  :  CHCH2CH3  - 
Propylidene-phenyl-hydrazone. 


C6H5NHN  :  C(CH8)COOC2H, 


■>  C6H4        CH  +  NH3 

\   /  * 
NH 

/3-Methyl-indol. 
/CHX 

C.COOC2H5 


->  C6H4 


Phenylhydrazone  of  Pyruvic  Ester. 

NH    +  NH3. 
a-Indol-carboxylic  Ester. 

Preparation  96.— Methyl  Ketol  (a-Methyl-indol). 

CH 


CH 
CH 


CH 


C 

!H  V.U 


CQHQN. 


131. 


C.CH, 


30  gms.  (1  mol.)  of  phenylhydrazine  are  mixed  with  18  gms.  (slightly 
more  than  1  mol.)  of  commercial  acetone  (B.P.,  56° — 58°).  The  mixture 
becomes  very  warm  and  a  good  deal  of  water  separates.  The  mixture 
is  heated  on  a  water  bath  for  15  minutes,  a  small  portion  being  occasionally 


CAKBON  TO  CARBON 


165 


tested  with  Fehling's  solution.  As  long  as  phenylhydrazine  is  present 
in  excess,  the  Fehling's  solution  is  reduced ;  more  acetone  is  then 
added  from  time  to  time  until  the  reducing  action  of  the  mixture  has 
almost  ceased.  The  turbid  oil  (crude  acetone-phenylhydrazone)  is  placed 
in  a  large  copper  crucible,  and  the  excess  of  acetone  removed  by  heating 
on  a  water  bath  for  \  hour.  200  gms.  of  dry  commercial  zinc  chloride 
are  next  added,  and  the  mixture  heated  on  the  bath  with  frequent  stirrmg. 
The  whole  is  then  heated  on  an  oil  bath  to  180°,  and  when  in  a  few  minutes 
the  mass  has  acquired  a  dark  colour  the  crucible  is  immediately  removed 
from  the  bath  and  stirred.  The  reaction  is  complete  in  a  short  time, 
and  can  be  followed  by  the  change  in  colour  of  the  fusion  and  the  evolution 
of  vapours.  The  dark  fused  mass  is  treated  with  3  J  times  its  weight  of 
hot  water,  and  distilled  in  steam  after  acidification  with  a  little  hydro- 
chloric acid.  The  methyl  ketol  distils  over,  slowly  but  completely,  as  a 
pale  yellow  oil  which  soon  solidifies.  This  is  filtered  off,  melted  to  free 
it  from  water  and  distilled.    It  must  be  kept  in  a  well-closed  bottle. 


Yield. — 55%  theoretical  (20  gms.).  Pale  yellow  crvstals  :  obnoxious 
odour  ;  M.P.  95°  ;  B.P.  750,  272°.    (A.,  234,  126.) 


CH3 


C6H5NHNH2  +  OC  =  C6H5NHN  :  C(CH3)2  +  H20. 


CH3 


CHAPTER  IX 


the  linking  of  hydrogen  to  carbon 

Hydrogen  Compounds 

Although  neither  so  numerous  nor  important  as  the  carbon  to  carbon 
reactions  discussed  in  Chapter  VIII.,  yet  a  number  of  reactions,  more 
particularly  a  number  of  those  classed  under  the  heading  of  reductions 
have  to  be  dealt  with  below.  Not  unnaturally  hydrocarbons  loom  largely 
among  the  products  ;  some  of  the  most  important  methods  of  preparing 
them  depend  on  the  reduction  of  derivatives  previously  obtained. 

Reaction  LVI.  Action  of  Water  on  certain  Metallic  Carbides.  (J.  C.  S., 
87,  1232). — This  reaction  has  an  important  and  well-known  application 
in  the  production  of  acetylene  on  an  industrial  scale.  Methane  can  be 
obtained  in  a  similar  way  from  aluminium  carbide. 

yC  CH 

Ca<|||  +  2H20  =  CaO  +  ||) 
XC  CH. 
A14C3  +  12H20  =  3CH4  +  4Ai(OH)3. 

Preparation  97. — Acetylene  (Ethin). 

CH 

III  C2H2.  26. 

CH. 

10  gms.  (1  mol.)  of  calcium  carbide  are  placed  in  a  shallow  layer  over 
sand  in  a  large  conical  flask  fitted  with  a  two-holed  rubber  stopper 
carrying  a  tap-funnel  and  a  delivery  tube.    Water  is  added  drop  by  drop 
from  the  tap-funnel.     The  gas  evolved  contains  among  other  impurities 
hydrogen  from  free  calcium,  siluretted  hydrogen  from  calcium  silicide, 
phosphoretted  hydrogen  from  calcium  phosphide,  and  acetaldehyde 
vapour  produced  by  condensation  of  acetylene  with  water.    The  gas  is 
purified  by  passing  it  through  (i.)  dilute  sulphuric  acid  ;  this  removes 
ammonia  ;  (ii.)  a  tower  packed  with  a  mixture  of  equal  parts  of  bleaching  I 
powder  and  quicklime  ;   this  removes  phosphorus  compounds  ;   (hi.)  a 
solution  of  cupric  chloride  acidified  with  dilute  sulphuric  acid  ;  (iv.)  a 
solution  of  ferric  chloride  similarly  acidified  ;  (v.)  a  solution  of  chromic  I 
acid  ;  all  these  remove  phosphorus  and  sulphur  compounds  ;  (vi.)  a  50%  j 
aqueous  solution  of  caustic  potash.    The  gas  is  collected  in  a  gas-holder, 
over  50%  aqueous  glycerol,  in  which  it  is  only  very  slightly  soluble.  I 
Before  collecting,  care  should  be  taken  that  all  air  has  been  removed  r 
from  the  apparatus  ;  during  the  filling  of  the  holder  the  rate  of  flow  of  I 

166 


THE  LINKING  OF  HYDROGEN  TO  CARBON  167 


liquid  from  it  should  be  adjusted  so  that  there  is  a  slightly  increased 
pressure  in  the  apparatus  ;  this  can  be  seen  from  the  height  of  liquid  in 
the  central  tube  of  the  gas-holder. 

The  purity  of  the  gas  is  tested  by  explosion  analysis  (J.  C.  S.,  84,  555)  ; 
the  ratio  contraction  on  explosion  ;  absorption  by  baryta  water  after 
explosion  should  lie  between  0-73  and  0-77  (theoretical  0-75).  Great  care 
must  be  taken  that  this  preparation  is  carried  out  in  the  absence  of  name, 
and  that  neither  the  apparatus  nor  the  collected  gas  is  exposed  to  direct 
sunlight,  which  decomposes  acetylene.  Also  the  cupric  chloride  solution 
employed  for  washing  should  be  kept  acid  ;  if  it  becomes  alkaline  the 
explosive  copper  acetylide  is  precipitated.  Should  this  occur  the  solution 
is  mixed  with  much  water  and  poured  away. 

CaC2  +  2H20  =  C2H2  +  CaO. 

Colourless  gas ;  when  pure  has  a  garlic-like  smell ;  at  N.T.P.  water 
dissolves  1  volume  ;  acetone  31  volumes  ;  explosive  limits  in  air  3 — 52%  ; 
in  oxygen  2—92%.    (J.  C.  S.,  87,  1232.) 

Methane  is  prepared  from  aluminium  carbide  and  dilute  hydrochloric 
acid  in  a  similar  apparatus.    It  is  purified  as  described  on  p.  176. 

Reaction  LVTI.  Action  of  jjHydrogen  in  the  presence  of  finely  divided 
Nickel  on  Aromatic  Compounds  (Sabatier-Senderens).  (C.  r.,  132,  210.) — 
The  addition  of  hydrogen  to  an  aromatic  compound  by  passing  its  vapour 
mixed  with  hydrogen  over  finely  divided  nickel  at  a  relatively  low  tempera- 
ture is  a  reaction  of  wide  and  important  application.  Although  nickel  is 
the  metal  most  usually  employed,  other  metals  can  also  act  as  hydrogen 
carriers.  The  method  is  chiefly  used  for  the  reduction  of  the  nucleus  in 
aromatic  compound^— hydrocarbons,  phenols,  amines,  etc.,  to  the  corre- 
sponding unsaturated  and  fully-saturated  paraffin  derivatives.  Ethylenic 
and  acetylenic  linkings,  aldehydes  and  ketones  can  also  be  reduced  in 
this  way,  and  the  reaction  has  been  applied  on  the  large  sc«le  to  the 
removal  of  the  unsaturation  ("  hardening  ")  of  fats  and  oils. 

Preparation  98. — Hexahydrobenzene  (cyclohexan). 

CH2 
H2C/\CH2 

H2C\^^/CH2 
CH2 

Preparation  of  the  Catalyst, 

Small  pieces  of  pumice  stone  of  a  convenient  size  are  soaked  in  a  con- 
centrated solution  of  nickel  nitrate  in  distilled  water,  and  heated  in  a  basin 
over  a  free  flame  until  the  nitrate  has  been  converted  into  the  oxide. 
Alternatively  the  pumice  is  impregnated  with  a  paste  of  its  own  weight 
of  nickel  oxide  and  distilled  water,  and  dried  on  a  water  bath.  The 
nickel  oxide  is  reduced  by  heating  in  a  current  of  pure,  thoroughly  dried 
hydrogen  in  a  combustion  tube.  The  arrangement  of  the  apparatus,  and 
the  preparation  and  purification  of  hydrogen  is  the  same  as  for  the  prepara- 


CRH 


84. 


168  SYSTEMATIC  ORGANIC  CHEMISTRY 


tion  of  reduced  copper  (see  p.  410).  The  pumice  is  loosely  packed  into 
the  combustion  tube  and  kept  in  position  by  asbestos  plugs.  The  air 
bath  is  maintained  at  about  280°  ;  it  is  tilted  slightly  forwards  so  that 
any  liquid  formed  may  run  down  into  the  receiver.  Ordinary  corks 
should  be  used,  and  not  rubber  stoppers  in  making  the  connections  to 
the  combustion  tube.  Unpurified  hydrogen  must  not  be  admitted,  as 
otherwise  the  catalyst  will  be  poisoned.  It  is  convenient  to  have  a  by- 
pass in  the  form  of  a  T-piece  between  the  copper  gauze  and  the  caustic 
soda  tower. 

At  first  the  hydrogen  escapes  through  the  by-pass.  After  the  air  has 
been  expelled  (a  sample  must  be  collected  and  tested)  as  far  as  the  T-piece, 
the  copper  gauze  tube  is  heated,  and  the  current  of  hydrogen  is  then 
diverted  through  the  tower  into  the  combustion  tube.  Some  should  also 
be  allowed  to  escape  through,  the  funnel  B  (Fig.  48)  to  remove  air  from 
its  stem.  When  the  air  has  all  been  expelled  as  before,  the  air  bath 
carrying  the  combustion  tube  is  heated.  Air  must  not  be  allowed  to  enter 
the  combustion  tube  from  now  until  the  end  of  the  experiment.  The 
reduction  of  the  nickel  oxide  will  take  at  least  a  week  ;  the  hydrogen  is 
passed  at  the  rate  of  about  300  c.cs.  per  minute.  The  reduction  is  accom- 
panied by  a  colour  change  from  black  to  a  greyish-yellow,  and  is  complete 
when  no  more  steam  is  evolved,  i.e.,  when  a  calcium  chloride  tube  at  the 
exit  end  of  the  combustion  tube  does  not  gain  in  weight  after  passing  the 
exit  gas  through  it  for  J  hour. 

Hydrogenation  of  Benzene. 

The  benzene  used  should  first  be  tested  for  thiophene  with  isatin  and 
cone,  sulphuric  acid,  and  then  redistilled  and  recrystallised ;  traces  of 


sulphur  and  chlorine  compounds  completely  inhibit  the  reaction.  The 
benzene  is  introduced  at  the  rate  of  about  7  c.cs.  per  hour  into  the  combus- 
tion tube  by  means  of  a  dropping-funnel,  B,  whose  stem,  drawn  out  to  a 
capillary,  passes  through  one  hole  of  the  double-holed  cork  at  A  (Fig.  48). 
The  quantity  of  benzene  used  is  obtained  by  weighing  the  quantity  in 
the  funnel  before  and  after  the  experiment.  The  temperature  of  the  air 
bath  should  be  180° — 190°,  and  the  hydrogen  should  be  passed  at  about 


<=  I  :.L;  H  SOU  _l 


Fig.  48. 


THE  LINKING  OF  HYDROGEN  TO  CARBON  169 


250  c.cs.  per  minute.  When  commencing  to  add  the  benzene  at  A,  air 
must  not  be  allowed  to  enter  the  tube  ;  the  vapour  issuing  from  the 
combustion  tube  is  condensed  in  a  flask  immersed  in  a  freezing  mixture. 
The  liquid  obtained  which  contains  a  little  unchanged  benzene,  when 
sufficient  has  been  collected,  is  treated  with  a  nitrating  mixture  of  sulphuric 
and  nitric  acid  (see  p.  262).  Cyclohexane  is  scarcely  affected  by  this 
mixture  while  benzene  is  rapidly  nitrated.  It  cannot  otherwise  easily 
be  separated  from  cyclohexane  ;  their  boiling  points  and  freezing  points 
are  almost  identical.  After  standing  for  1  hour  the  top  layer  of  oil  is 
separated,  well  washed  with  water,  and  dried  for  24  hours  over  calcium 
chloride.  It  is  fractionated,  and  the  fraction  78° — 85°  redistilled  and 
collected  between  80°— 82°. 

C6H6  +  3H2  =  C6H12. 

Yield. — 80%  theoretical.  Calculated  on  the  benzene  volatilised 
(8-5  gms.  cyclohexane  per  10  gms.  benzene).  Almost  theoretical  allowing 
for  unchanged  benzene  (11  gms.  cyclohexane  per  10  gms.  benzene). 
Colourless  liquid  ;  insoluble  in  water  ;  B.P.  81°.    (C.  r,  132,  210.) 

Preparation  99.— Hexahydrophenol  (cyclohexanol). 

CHOH 

H2C/\CH2 

C6H120.  100. 

CH2 

The  apparatus  is  as  in  Preparation  98,  except  that  in  front  of  the  catalyst 
tube  is  inserted  a  small  distilling  flask  weighed  before  and  after  the  experi- 
ment containing  100  gms.  of  pure  redistilled  phenol.  Hydrogen  enters 
by  means  of  a  one-holed  cork  in  the  neck  of  the  flask  and  leaves  by  the 
side  tube,  which  fits  into  a  one-holed  cork  at  A  (Fig.  48).  During  the 
reduction  (p.  167)  of  the  nickel  oxide  the  tube  by  which  the  hydrogen 
enters  the  flask  is  raised  a  little  above  the  surface  of  the  phenol.  After 
reduction  is  complete  and  the  temperature  of  the  catalyst  has  been 
reduced  to  180° — 190°,  the  phenol  in  the  flask  is  heated  almost  to  its 
boiling  point,  and  the  hydrogen  delivery  tube  pushed  well  down  into  the 
liquid.  Care  must  be  taken  that  phenol  does  not  condense  in  the  tube, 
and  that  only  the  vapour  passes  over.  When  sufficient  liquid  has  con- 
densed in  the  receiver,  it  is  shaken  with  caustic  soda  solution  to  remove 
unchanged  phenol,  extracted  with  ether,  and  the  extract  dried  over 
anhydrous  potassium  carbonate  for  24  hours.  The  ether  is  removed  on  a 
water  bath,  and  the  residue  distilled  ;  the  fraction  166° — 174°  is  collected 
and  refractionated  between  169° — 171°. 

C6H5OH  +  3H2  =  C6HuOH. 

Yield. — Almost  theoretical  (10-5  gms.  of  hexahydrophenol  per  10  gms. 
of  phenol).  Colourless  liquid  ;  aromatic  smell,  insoluble  in  water  ;  B.P. 
17°.    (C.  r.,  132,  210.) 


170  SYSTEMATIC  ORGANIC  CHEMISTRY 


Hexahydro toluene,  hexahydrocresol,  etc.,  may  be  obtained  by  methods 
exactly  similar  to  the  foregoing. 

Reaction  LVIII.  (a)  Reduction  of  Phenols  and  Quinones  by  Distillation 
with  Zinc  Dust.  (A.,  140,  205.) — When  certain  aromatic  oxygen  com- 
pounds (phenols,  naphthols,  quinones,  etc.),  are  heated  with  zinc  dust, 
they  are  reduced  to  the  corresponding  hydrocarbons.  Thus,  phenol  yields 
benzene,  the  naphthols,  naphthalene ;  while  anthracene  can  be  obtained 
from  anthraquinone  or  its  hydroxy  derivatives,  alizarin,  or  quinizarin. 
It  was  in  this  way  that  alizarin  was  first  proved  to  be  an  anthracene 
derivative.    (B.,  1,  43.) 

CO  OH 

/\/\/\OH  /\/\/\ 

|     +  4Zn  =i  1      I  +  4ZnO. 

coV/ 

Pkepakation  100. — Anthracene  (s-Dibenz-benzene). 


178. 


Pieces  of  porous  pumice  stone  of  a  size  that  will  conveniently  pass  into 
a  combustion  tube  are  added  to  a  paste  prepared  from  100  gms.  of  good 
zinc  dust  and  30  c.cs.  of  alcohol,  and  are  stirred  round  so  that  they  become 
covered  with  the  paste.  They  are  removed  from  the  paste  with  tongs, 
and  heated  in  a  porcelain  dish  with  constant  motion  over  a  free  flame 
until  the  alcohol  is  evaporated.  A  hard  glass  combustion  tube,  70  cms. 
long,  is  drawn  out  at  one  end  to  a  narrow  tube,  the  narrowed  end  is  closed 
by  a  loose  plug  of  asbestos,  and  a  layer  of  zinc  dust,  5  cms.  long,  is  placed 
next  to  the  plug,  then  comes  a  mixture  of  2  gms.  of  quinizarin  (see  p.  102), 
alizarin,  or  anthraquinone  with  20  gms.  (excess)  of  zinc  dust,  and  finally 
a  layer  of  pumice  zinc  dust,  30  cms.  long.  After  a  canal  has  been  formed 
over  the  zinc  dust  by  placing  the  tube  in  a  horizontal  position  and  tapping 
it,  the  latter  is  transferred  to  a  combustion  furnace,  tilted  forwards,  as 
in  a  nitrogen  estimation  (see  p.  451)  and  a  rapid  current  of  dry  hydrogen 
(see  p.  410)  is  passed  through  the  tube  without  heating.  The  open  end 
of  the  tube  is  closed  by  a  one-holed  cork,  and  the  issuing  gas  led  to  a 
draught  pipe.  After  the  gas  has  been  passed  for  some  time  a  test-tube 
of  the  issuing  gas  is  collected  over  water  at  intervals,  and  a  light  applied 
to  the  mouth  of  the  test-tube  at  least  12  ft.  from  the  apparatus.  When 
the  contents  of  the  tube  burn  quietly,  all  the  air  has  been  displaced  from 
the  apparatus.  The  gas  current  is  then  diminished  to  about  150  c.cs. 
per  minute,  and  the  pumice  zinc  dust  is  heated  with  small  flames.  (On 
no  account  must  the  apparatus  be  heated  until  all  the  air  has  been  dis- 
placed.) The  heating  is  gradually  increased  from  the  front  backwards, 
until  finally  the  tube  is  heated  as  strongly  as  possible.  The  rear 
layer  of  5  cms.  of  zinc  dust  is  next  similarly  heated,  and  when  this  glows, 


THE  LINKING  OF  HYDROGEN  TO  CARBON 


171 


the  mixture  of  anthracene  derivative  and  zinc  dust  is  gradually  heated, 
all  being  done  as  in  the  estimation  of  nitrogen.  The  anthracene  formed 
condenses  to  crystals  in  the  forward  cool  part  of  the  tube.  After  the 
reaction  is  complete,  a  rapid  current  of  hydrogen  is  passed  while  the  tube 
is  cooling  ;  when  cold  the  part  containing  the  anthracene  is  broken  off, 
and  the  substance  removed  with  a  small  spatula  ;  it  is  purified  by  sublima- 
tion (see  p.  28). 

CO  OH 

CH 

+  5H2  =  C,h/  I  \c.H4  +  4H20. 

CO  OH 

Yield. — Almost  theoretical  (1-5  gms.).  Colourless  crystals  ;  insoluble 
in  water  ;  soluble  in  warm  benzene  and  in  glacial  acetic  acid  ;  M.P.  213°  ; 
B.P.  351°  ;  M.P.  of  picrate,  138°.    (A.,  140,  205.) 

It  is  better  to  use  alcohol  in  making  zinc  dust  paste,  for  if  there  is  much 
oxide  present  in  the  dust  a  great  deal  of  heat  may  be  evolved  on  adding 
water,  and  much  oxidation  of  the  metal  occur. 

The  following  is  one  of  the  methods  employed  for  the  separation  of 
pure  anthracene  from  the  coal  tar  fraction  containing  it.  Carbazole  and 
phenanthrene  are  the  chief  impurities  present. 


Purification  of  Crude  Anthracene. 

Crude  anthracene  (about  40%)  is  mixed  with  1\  times  its  weight  of 
benzene  or  solvent  naphtha  (90%  at  160°)  in  a  vessel  fitted  with  a 
mechanical  stirrer.  Sodium  nitrite  to  one-tenth  of  the  weight  of  crude 
anthracene  taken,  is  dissolved  in  10  times  its  weight  of  water,  and  sufficient 
10%  sulphuric  acid  (7-2  gms.  for  each  1  gm.  of  10%  nitrite)  to  decompose 
this  quantity  of  nitrite  is  added  to  the  benzene — anthracene  mixture 
and  the  temperature  maintained  at  25°.  The  nitrite  solution  is  then  run 
in  at  such  a  speed  that  no  red  fumes  escape.  When  all  the  solution  has 
been  added  the  mixture  is  filtered  at  the  pump.  The  nitrate  consists 
of  two  layers,  one  of  sodium  sulphate  solution  and  one  of  solvent  naphtha, 
or  benzene  containing  the  impurities  such  as  nitroso-carbazol.  The 
purified  anthracene  on  the  filter  is  washed  with  benzene  or  solvent 
naphtha  ;  this  latter  on  a  large  scale  is  used  for  the  final  treatment  of  a 
fresh  lot  of  crude  anthracene.  The  initial  benzene  or  solvent  naphtha, 
after  separation  from  the  aqueous  solution,  is  recovered  by  distillation. 
The  anthracene  from  this  treatment  will  be  about  80%  pure.  It  may 
be  purified  to  95%  by  crystallising  from  heavy  bases  (pyridine,  etc.), 
and  is  finally  raised  by  sublimation  and  recrystallisation  from  benzene 
to  98%.  (For  the  estimation  of  purity,  see  p.  494.)  (C.  T.,  23,  8,  21  ; 
D.R.P.,  122852.) 

Reaction  LVIII.  (6)  Reduction  of  Aromatic  Ketones  to  the  corre- 
sponding Hydrocarbons  by  treatment  with  Hydriodic  Acid  or  with  Sodium 
in  Alcoholic  Solution.    (B.,  7,  1624 ;  31,  999.)— Two  methods  for  the 


172  SYSTEMATIC  ORGANIC  CHEMISTRY 


reduction  of  aromatic  ketones  to  the  corresponding  hydrocarbons  are 
exemplified  below.  Method  I.  using  hydriodic  acid  is  a  standard  method 
for  the  reduction,  especially  the  complete  reduction,  of  an  organic  com- 
pound ;  the  sodium-alcohol  method  given  in  II.  is  not  so  universally 
applicable — it  is  a  milder  reducing  agent  and  more  selective  ;  thus,  it 
was  used  by  Bamberger  in  his  researches  on  the  formula  of  naphthalene, 
to  reduce  one  only  of  the  two  rings  in  that  compound  and  its  derivatives. 
The  nickel  oxide-hydrogen  method  can  be  applied  here,  as  also  to  the 
reduction  of  mixed  aliphatic-aromatic  ketones  ;  aliphatic  ketones  are 
best  directly  reduced  by  Method  I. 
Peepaeation  101. — Diphenylmethane  (Benzyl-benzene.) 

C6H5.CH2C6H5.       C13H12.  168. 

Method  I. — 10  gms.  (1  mol.)  of  benzophenone,  12  gms.  (nearly  2mols.) 
of  hydriodic  acid  (B.P.  127°)  and  2  gms.  (more  than  1  atom)  of  red  phos- 
phorus are  heated  together  in  a  sealed  tube  for  6  hours  at  160°  (see 
p.  38).  The  reaction  mixture  is  extracted  with  ether  and  the  extract 
washed  with  water  several  times.  It  is  then  filtered,  dried  over  calcium 
chloride  for  24  hours,  the  ether  removed  on  a  water  bath  and  the  residue 
distilled. 

C6H5.CO.C6H5  +  4HI  =  C6H5.CH2.C6H5  +  H20  +  2I2. 
Yield.- Theoretical  (9  gms.)    (B.,  7,  1624.) 

Method  II. — 10  gms.  (1  mol.)  of  benzophenone  are  refluxed  with  100 
gms.  (excess)  of  alcohol,  and  10  gms.  (excess)  of  sodium  wire  are  gradu- 
ally added  through  an  addition  tube  (see  p.  47)  to  the  boiling  liquid. 
When  the  solution  of  the  sodium  is  complete  the  liquid  in  the  flask  is 
cooled,  saturated  with  carbon  dioxide,  poured  into  cold  water  and  the 
whole  extracted  with  benzene.  The  extract  is  dried  for  24  hours  over 
calcium  chloride,  the  benzene  removed  on  a  water  bath,  and  the  residue 
distilled  under  reduced  pressure,  the  fraction  174° — 176°  at  80  mms.  being 
retained. 

C6H5.CO.C6H5  -f-  2H2  =  C6H5.CH2.C6H5  +  H20. 

Almost  theoretical  (8*5  gms.).  Colourless  oil ;  orange  like  odour,  solidifies 
to  needle-shaped  crystals ;  M.P.  26° ;  B.P.  760,  263° ;  B.P.  80,  175°. 
(B.,  31,  999.) 

Reaction  LIX.  Reduction  o£  a  Primary  Aryl  Hydrazine  to  the  corre- 
sponding Hydrocarbon  by  the  action  of  Copper  Sulphate  or  Ferric  Chloride. 

(B.,  18,  90,  786).  When  a  primary  aryl  hydrazine  is  boiled  with  neutral 
copper  sulphate  or  ferric  chloride,  or  treated  with  alkaline  copper  sulphate 
in  the  cold,  the  hydrazine  radical  is  replaced  by  hydrogen,  the  corre- 
sponding aryl  hydrocarbon  being  formed. 

C6H5NH.NH2  +  2CuO  =  C6H6  +  N2  +  H20  +  Cu20. 

This  reaction  can  be  employed  to  remove  a  primary  amino  group  from 
an  aromatic  compound,  especially  when  the  ordinary  method  of  direct 
reduction  of  the  diazonium  compound  by  sodium  stannite  or  alcohol  is 


THE  LINKING  OF  HYDROGEN  TO  CAKBON  173 


not  applicable.    Although  in  the  application  of  this  method  the  hydrazin , 
can  be  prepared  as  the  hydrochloride,  and  reduced  in  the  same  solution 
yet  it  is  better  to  isolate  the  free  base  and  oxidise  it  separately,  since  in, 
the  oxidation  of  the  hydrochloride  there  is  a  tendency  for  the  hydrazine 
radical  to  be  replaced  by  chlorine. 

Reaction  LX.  Action  of  Water  on  Magnesium  Alkyl  or  Aryl  Halides 
(Grignard).  (B.,  39,  634.) — When  a  Grignard  compound  is  treated  with 
water  or  other  substance  containing  a  hydroxyl  group  hydrolysis  occurs, 
and  the  corresponding  hydrocarbon  is  obtained. 

C6H5.Mg.I  +  H20  =  C6H6  +  OH.Mg.I. 
C6H5MgI  +  C2H5OH  =  C6H6  +  C2H5O.MgI. 

This  reaction  is  of  theoretical  rather  than  practical  importance. 
Preparation  102. — Triphenyl  Methane  ( ( (  Di-phenyl)-methyl)-benzene) 

HC(C6H5)3.       C19H16.  244. 

10  gms.  (1  mol.)  of  triphenylmethyl  chloride  and  0-1  gms.  of  iodine  are 
dissolved  with  gentle  heating  in  50  c.cs.  of  sodium-dried  ether  in  a  dry 
round-bottomed  flask  of  500  c.cs.  capacity,  fitted  with  a  long  reflux  con- 
denser, 2  gms.  (excess)  of  clean,  dry  magnesium  filings  or  small  pieces  of 
the  ribbon  are  added  (see  p.  68). 

A  slow  stream  of  well-dried  hydrogen  is  passed  through  the  liquid  by 
means  of  a  tube  through  the  cork  to  the  bottom  of  the  flask  ;  the  hydrogen 
coming  from  the  top  of  the  reflux  condenser  must  be  led  to  a  good  draught 
pipe  (the  flask  heated  on  a  water  bath  to  vigorous  boiling,  and  the  water 
bath  removed).  After  the  removal  of  the  water  bath  the  flask  is  wrapped 
in  a  cloth  to  conserve  the  heat  of  reaction,  which  is  then  sufficient  to  keep 
the  ether  boiling  for  about  1  hour,  by  which  time  bright  yellow  crystals 
of  the  magnesium  compound  have  separated.  The  whole  is  again  heated 
to  boiling  on  a  water  bath  for  1  hour,  and  then  all  the  water  is  run  out  of 
the  condenser.  The  ether  evaporates  and  the  solid  magnesium  compound 
remains.  To  it  is  added  after  increasing  the  rate  of  passage  of  hydrogen 
with  complete  exclusion  of  air  60  c.cs.  (excess)  of  distilled  water,  and  then 
in  small  portions,  40  gms.  of  cone,  sulphuric  acid.  The  flask  is  well 
shaken  and  the  contents  boiled  on  a  wire  gauze  for  15  minutes.  The 
yellow  crystalline  cake  of  the  magnesium  compound  at  first  swims  on 
the  surface,  but  gradually  decomposes  to  a  surface  layer  of  homogeneous 
liquid.  The  reaction  is  complete  when  all  the  magnesium  compound 
has  disappeared  and  the  whole  is  clear.  Towards  the  end  the  flask  is 
shaken  vigorously  at  short  intervals  to  prevent  spurting  of  the  accumu- 
lating oil.  The  flame  is  removed,  the  hydrogen  stream  shut  off,  and 
150  c.cs.  of  pure  benzene  added  to  the  liquid  while  still  hot,  the  whole 
being  vigorously  shaken.  The  benzene  solution,  which  is  coloured  red  with 
iodine^  is  separated  and  treated  in  turn  with  warm  water,  warm  aqueous 
caustic  soda,  warm  sodium  thiosulphate  solution,  and  again  with  warm 
water.  The  turbid  liquid  is  shaken  with  calcium  chloride,  and  warmed 
until  it  becomes  clear.  It  is  filtered  hot,  allowed  to  stand  over  fresh 
calcium  chloride  for  24  hours,  again  filtered  hot,  and  evaporated  on  a  water 


174  SYSTEMATIC  ORGANIC  CHEMISTRY 


bath  to  a  bulk  of  10  c.cs.  On  cooling  triphenylmethane  crystals  containing 
benzene  of  crystallisation  separate.  These  crystals  slowly  lose  benzene 
on  standing  and  more  quickly  on  heating  on  a  water  bath.  The  hydro- 
carbon is  finally  recrystaUised  from  hot  alcohol. 

(C6H5)3CC1  ->  (C6H5)3CMgCl  ->  (C6H5)3CH. 

Yield— 90%  theoretical  (8  gms.).  Colourless  plates  ;  soluble  in  benzene 
and  in  hot  alcohol ;  M.P.  93°  ;  B.P.  300°  ;  separates  from  benzene  in 
crystals  containing  1  mol.  of  benzene  of  crystallisation ;  M.P.  76°. 
(B.,  39,  634.) 

Reaction  LXI.  Reduction  of  Diazonium  Compounds  to  the  correspond- 
ing Hydrocarbon.  (A.,  137,39;  B.,  22,  587  ;  35,162;  36,815,2065;  40, 
858).  When  a  diazonium  compound  is  boiled  with  an  alcohol,  oxidation 
of  the  latter  to  the  corresponding  aldehyde  and  simultaneous  replacement 
of  the  diazo  group  by  hydrogen  occurs. 

E.N  1  N  +  C2H5OH 

CI  =  EH  +  N2  +  HC1  +  CH3CHO. 

This  is  the  classical  method  of  reducing  diazonium  compounds,  but 
other  reducing  agents,  notably  sodium  stannite,  give  better  results  ;  the 
alcohol  always  tends  to  form  with  the  diazonium  compound  more  or 
less  of  the  corresponding  mixed  ether,  unless  a  large  number  of  negative 
groups  be  present.  Hypophosphorous  acid  and  alkaline  sodium  hydro- 
sulphite  also  give  good  yields  with  certain  types  of  compounds. 

The  method  is  much  used  to  remove  the  amino  group  from  an  aromatic 
nucleus,  and  has  had  some  theoretically  important  applications. 

Preparation  103. — s-Tri-bromobenzene  (1:3:  5-Tri-bromobenzene). 

Br 

/\ 

I      I  C6H5Br3.  315. 

Br^/'Br 

50  gms.  (1  mol.)  of  finely  powdered  s-tribromaniline  (see  p.  349)  are 
treated  with  300  c.cs.  (excess)  of  absolute  alcohol  and  75  c.cs.  of  benzene 
added  to  insure  complete  solution.  20  c.cs.  (excess)  of  cone,  sulphuric 
acid  are  run  in  ;  should  a  precipitate  form,  it  is  redissolved  by  the  addition 
of  more  benzene.  20  gms.  (excess)  of  pure  finely  powdered  sodium 
nitrite  are  added  to  the  hot  liquid  as  rapidly  as  possible  without  the 
reaction  becoming  too  violent,  and  the  whole  heated  until  effervescence 
ceases.  After  standing  over-night  the  precipitate  is  filtered,  washed  at 
the  pump  with  hot  water  until  the  washings  give  no  precipitate  with 
barium  chloride,  dried  on  a  porous  plate  and  recrystallised  from  absolute 
alcohol. 

NaN02  C2H5OH 

C6H2Br3NH2  —  >  C6H2Br3.N2.S04  >  C6H3Br3. 

H2S04 

Yield. — Almost  theoretical  (47.  gms.).  Colourless  prisms  ;  insoluble 
m  water  ;  M.P.,  119°.    (B.,  22,  587.) 


THE  LINKING  OF  HYDROGEN  TO  CARBON  175 


Preparation  104.— Diphenyl  (Phenyl-benzene). 

C6H5.C6H5.       C12H10.  154. 

30  gms.  (1  mol.)  of  benzidine  are  added  to  60  c.cs.  cone,  hydrochloric 
acid  and  400  c.cs.  water.  The  whole  is  heated  until  the  benzidine  is 
dissolved.  After  cooling  it  is  diazotised  with  23  gms.  (2  mols.)  of  sodium 
nitrite  (see  p.  366).  To  the  ice-cold  tetrazonium  solution  is  added 
I  350  c.cs.  of  commercial  hypophorous  acid  (D.  1*15).  After  standing  for 
several  days  in  an  ice  chest,  until  no  more  solid  separates,  the  diphenyl  is 
filtered  off,  treated  with  dilute  caustic  soda  solution  and  steam  distilled. 
It  is  then  recrystallised  from  absolute  alcohol. 

NH2C6H4.C6H4NH2  ->  C1N2C6H4.C6H4N2C1  ->  C6H5.C6H5. 

Yield. — 60%  theoretical  (15  gms.).  Colourless  leaflets  ;  insoluble  in 
cold  alcohol ;  M.P.  71°  ;  B.P.  254°.    (B.,  35,  162.) 

Hypophorous  acid  may  be  prepared  by  digesting  150  gms.  finely 
powdered  calcium  hypophosphite  with  45  c.cs.  of  cone,  sulphuric  acid, 
and  500  c.cs.  water  for  1  hour  at  80°,  and  removing  the  calcium  sulphate 
by  filtration. 

Reaction  LXII.   Direct  Reduction  of  Halogen  Compounds.    (J.  C.  S., 

(1902),  535).  A  very  useful  method  for  the  preparation  of  hydrocarbons, 
more  especially  of  aliphatic  hydrocarbons  consists  in  replacing  the  halogen 
atom  of  a  halogen  compound  by  an  atom  of  hydrogen. 

RC1  +  H2  =  EH  +  HC1. 

The  reducing  agents  usually  employed  are  phosphorus  and  hydriodic 
acid,  or  the  zinc-copper  or  the  aluminium-mercury  couple.  The  method 
of  using  the  first  of  these  is  given  on  p.  186. 

The  couples  have  the  advantage  of  readily  yielding  a  pure  gas,  and 
are  of  wide  application. 

Methane  can  be  prepared  from  methyl  iodide,  or  chloroform,  etc., 
ethane  from  ethyl  iodide,  propane  from  propyl,  and  isopropyl  iodides, 
and  so  on. 

The  following  will  illustrate  their  use  : — 

Preparation  105. — Methane  (Methyl-hydride). 

H 

I 

H — C — H.       CH4.  16. 

I 

H 

To  one  limb  of  a  wide  U  -tube  cooled  in  water  and  filled  with  the  zinc- 
copper,  or  the  aluminium-mercury  couple  is  attached  a  small  tap-funnel, 
and  to  the  other  a  small  reflux  condenser.  The  zinc-copper  couple  is 
prepared  by  placing  30  gms.  (excess)  of  zinc  in  an  aqueous  solution  of 
copper  sulphate  until  the  surface  of  the  metal  is  covered  with  a  film  of 
metallic  copper.  The  couple  is  washed  with  water  and  then  with  absolute 
alcohol.    The  aluminium-mercury  couple,  which  gives  a  better  yield  of 


176 


SYSTEMATIC  ORGANIC  CHEMISTRY 


gas,  is  prepared  by  immersing  20  gms.  (1  atom)  of  small  pieces  of  sheet 
aluminium  in  mercuric  chloride  solution  until  a  film  of  mercury  covers 
the  surface  of  the  aluminium,  which  is  washed  as  above.  100  c.c.  (excess) 
of  methyl  alcohol  (acidified  with  2  drops  of  dilute  sulphuric  acid  if  the 
zinc-copper  couple  be  used)  are  poured  on  to  the  couple  in  the  U-tube, 
and  50  gms.  of  methyl  iodide  are  added  gradually  from  the  funnel  so  that 
the  reaction  does  not  become  too  violent  nor  the  couple  too  hot.  With 
the  aluminium-mercury  couple  the  reaction  is  especially  vigorous,  and 
good  cooling  is  required.  The  gas  is  washed  in  worms  containing  (1)  dis- 
tilled water  ;  (2)  sodium  methoxide  dissolved  in  methyl  alcohol — 2 
worms  ;  (3)  distilled  water  ;  (4)  fuming  sulphuric  acid — 2  worms  ; 
(5)  cone,  sulphuric  acid— 2  worms  ;  (6)  distilled  water ;  (7)  50% 
caustic  soda  solution — 2  worms.  Cone,  sulphuric  acid  is  used  to  condense 
the  acid  mist  from  the  fuming  sulphuric  acid  washings  ;  distilled  water 
is  always  inserted  between  worms  containing  liquids,  which  will  react 
violently  if  mixed.  The  gas  is  then  passed  through  a  U-tube  heated 
in  boiling  water  and  containing  palladium  black  to  adsorb  hydrogen,  of 
which  usually  about  1%  is  present.  Alternatively,  palladium  oxide  may 
be  used  in  the  tube  to  oxidise  the  hydrogen.  The  gas  is  collected  in  a 
gas-holder  over  50%  aqueous  glycerol,  which  does  not  dissolve  methane, 
under  a  slight  excess  pressure,  as  described  in  Preparation  97,  unless 
the  dry  gas  be  required,  when  the  gas  is  collected  over  mercury  or  cone, 
sulphuric  acid,  being  first  dried  by  passage  through  two  U -tubes  contain- 
ing phosphorus  pentoxide.  Completely  to  free  it  from  hydrogen  three  or 
four  treatments  with  palladium  or  its  oxide  will  be  necessary.  The  gas 
obtained  in  this  way  is  pure  provided  care  be  taken  that  all  air  has  been 
swept  out  of  the  apparatus  before  collection  is  begun.  With  proper 
precautions,  the  ratio-contraction  on  explosion  to  absorption  by  baryta 
water  after  explosion  should  always  be  between  1-99  and  2-01,  the 
theoretical  value  being  2-00. 

CH3I  +  Zn  +  CH3OH  =  ZnI(OCH3)  +  CH4. 
3CH3I  +  2A1  +  3CH3OH  =  3CH4  +  Al2I3(OCH3)3. 

Colourless  odourless  gas ;  solubility  in  water  at  N.T.P.  =  5-25  ; 
B.P.  76°,  —  164°  ;  M.P.  -  184°  ;  explosive  limits  :  in  oxygen,  5—60%, 
in  air,  6—13%.    (J.  C.  S.,  81,  535.) 

Purification  by  Fractional  Liquefaction  or  Evaporation. 

If  liquid  air  be  available,  the  hydrogen  in  the  methane  prepared  above 
is  best  removed  by  fractional  distillation.  The  following  is  an  outline  of 
the  method  (see  Fig.  49). 

The  gas  from  the  gas-holder  is  passed  through  a  series  of  U-tubes  con- 
taining phosphorus  pentoxide,  then  through  a  small  bulb  B.  When  all 
the  air  has  been  driven  out  of  the  apparatus,  a  vacuum  vessel  containing 
liquid  air  is  brought  below  B  and  gradually  raised  so  as  slowly  to  increase 
the  cooled  surface  of  the  bulb.  The  methane  condenses  rapidly  in  B, 
hydrogen  passing  away  through  C.    When  A  is  almost  empty  of  gas,  the 


THE  LINKING  OF  HYDROGEN  TO  CARBON  177 


remainder  is  run  away  by  means  of  the  three-way  tap  D.  Meanwhile  the 
liquid  air  container  is  raised  or  lowered  around  B,  so  that  the  liquid  in  B 
gently  boils.  When  about  one-fifth  has  boiled  away  C  is  closed,  and  a 
small  amount  of  gas  allowed  to  pass  away  through  D.  Connection  is  then 
made  to  the  gas-holder,  which  is  slowly  filled  under  a  pressure  slightly 
above  atmospheric.  If  preferred,  the  methane  may  be  distilled  into 
another  holder  through  C,  and  the  gas  from  several  holders,  such  as  A, 
purified  and  collected  in  one  holder.  Great  care  must  be  taken  in  manipu- 
lating the  liquid  air  container,  so  that  the  liquid  in  B  boils  gently  ;  if  the 


B  Fig.  49. 


vacuum  vessel  be  lowered  too  rapidly,  vigorous  boiling  will  occur,  and  a 
great  pressure  generated  in  the  apparatus.  The  last  traces  of  gas  in  B 
are  not  collected. 

This  process  can  be  repeated  if  a  very  pure  gas  is  required.  In  each 
operation  about  one-third  of  the  original  gas  is  lost.  To  make  quite 
certain  that  the  gas  which  is  being  collected  is  pure,  a  platinum  resistance 
thermometer  may  be  enclosed  in  the  liquefaction  bulb,  and  the  tempera- 
ture determined  during  the  operation,  as  in  the  fractional  distillation  of 
any  other  liquid.  This  is  more  important  in  preparing  the  higher  hydro- 
carbons pure. 

The  methods  of  fractional  liquefaction  and  distillation  have  very  many 
similar  and  important  applications  in  the  chemistry  of  gases. 


s.o.c. 


CHAPTER  X 


hydrogen  to  carbon 
Hydroxy  Compounds 

Alcohols  and  Phenols 

The  reactions  discussed  below  are  based  on  the  reduction  of  the  group — 

I  I 
_ C  =  0     to     — C — OH. 


Such  reactions  comprise  practically  all  those  in  which  hydrogen  is 
linked  to  carbon  to  produce  of  necessity  a  hydroxy  compound. 

Reaction  LXIII.  Combined  Oxidation  and  Reduction  of  Aromatic 
Aldehydes  under  the  influence  of  Caustic  Alkalis  (Cannizzaro).  (B.,  14, 
2394.) — When  the  lower  aliphatic  aldehydes  are  treated  with  caustic 
alkalis,  resinification  quickly  occurs  ;  aromatic  aldehydes,  however,  and 
some  of  the  higher  aliphatic  aldehydes  behave  differently,  two  molecules 
smoothly  interacting  to  give,  by  simultaneous  oxidation  and  reduction,  one 
molecule  each  of  the  corresponding  acid  and  alcohol. 

KOH 

E.CHO  +  R.CHO  >    KCH2OH  +  RCOOH. 

This  method  is  frequently  used  for  the  preparation  of  aromatic  alcohols 
from  the  corresponding  aromatic  aldehydes  which  can  usually  be  readily 
obtained. 

Preparation  106. — Benzyl  Alcohol  (Phenyl-methanol). 

C6H5CH2OH.       C7H80.  108. 
and  Benzoic  Acid  (phenyl-methan  acid) 

C6H5COOH.       C7H602.  122. 

30  gms.  (2  mols.)  of  freshly  distilled  benzaldehyde  are  mechanically 
shaken  in  the  cold  with  45  gms.  (excess)  of  a  60%  solution  of  caustic 
potash  until  a  permanent  emulsion  is  formed.  The  mixture  is  allowed  to 
stand  for  24  hours,  during  which  time  much  potassium  benzoate  separates. 
Owing  to  the  presence  of  cone,  alkali,  a  glass  stopper  must  not  be  used 
to  close  the  shaking  bottle.  Water  is  added  until  a  clear  solution  is 
obtained,  which  is  then  extracted  four  times  with  ether.  The  extract 
which  contains  the  benzyl  alcohol  formed  is  shaken  with  cone,  sodium 
bisulphite  solution  (see  p.  506)  to  remove  traces  of  benzaldehyde,  washed 
with  dilute  caustic  soda  and  with  water  and  filtered.  The  ether  is  removed 

178 


THE  LINKING  OF  HYDROGEN  TO  CARBON 


179 


on  a  water  bath,  and  the  residue  fractionated,  the  fraction  204° — 208° 
being  redistilled  to  give  pure  benzyl  alcohol. 

The  alkaline  solution  from  which  benzyl  alcohol  has  been  extracted  is 
carefully  neutralised,  and  acidified  with,  at  first,  concentrated,  and  then 
dilute  hydrochloric  acid.  The  precipitated  benzoic  acid  is  recrystallised 
from  hot  water. 

2C6H5CHO  +  KOH  =  C6H5CH2OH  +  C6H5COOK. 

Yield. — 90%  theoretical  of  both  compounds  (benzyl  alcohol,  13-5  gms.  ; 
benzoic  acid,  15-5  gms.). 

Benzyl  Alcohol. — Colourless  oil  somewhat  soluble  in  water  ;  faintly 
aromatic  odour  ;  B.P.  206-5  ;  D.  154*  1-05. 

Benzoic  Acid. — Colourless  needles  ;  soluble  in  hot  water,  alcohol,  ether  ; 
melts  and  sublimes  on  heating  ;  can  be  distilled  in  steam  ;  M.P.  122°  ; 
B.P.  250°.    (B.,  14,  2394.) 

Reaction  LXIV.  (a)  Reduction  of  Aldehydes  and  Ketones  to  the  corre- 
sponding Alcohols  by  the  use  of  Alkaline  Reducing  Agents.  (B.,  31,  1003  ; 
J.  pr.,  [2],  33,  184  ;  [2],  76,  137.)— The  alkaline  reducing  agent  most 
usually  employed  is  sodium  amalgam  and  water,  especially  to  obtain 
polyhydric  alcohols  from  the  corresponding  sugars  ;  here  it  is  easily 
applied  owing  to  the  solubility  of  the  sugars  in  water.  But  even  if  the 
ketone  or  aldehyde  be  not  soluble  in  water,  the  amalgam  can  be  allowed 
directly  to  act  on  the  moist  substance,  or  the  latter  can  be  dissolved  in 
ether  or  benzene,  and  the  amalgam  and  water  gradually  added. 
Aluminium  amalgam  and  water  can  also  be  employed  in  a  similar  way. 
Sodium  and  alcohol  (see  also  Reaction  CLXXIV.)  are  generally  used  in 
the  aromatic  series.  In  reducing  ketones,  especially  aliphatic  ketones,  there 
is  always  more  or  less  pinacone  formation ;  this  is  not  so  marked  in  the 
aromatic  series,  especially  if  acid  reducing  agents  be  not  used  (see  p.  50). 
Here  zinc  dust  and  caustic  soda  or  ammonia,  and  alcoholic  sodium 
hydrosulphite  give  good  results.  The  Sabatier- Sender  ens  reaction  can  also 
be  employed  (see  p.  167). 

Pkepaeation  107. — Dulcitol  (Hexahydroxyhexan  H  [-)• 

CH2OH.(CHOH)4CH2OH.       C6H1406.  182. 

10  gms.  (1  mol.)  of  galactose  dissolved  in  100  gms.  of  water  are  shaken 
in  a  stout  500-c.c.  stoppered  bottle  with  30  gms.  of  2J%  sodium  amalgam 
(see  p.  505)  until  the  first  reaction  has  ceased.  Every  10  minutes  the 
liquid  is  neutralised  with  10%  sulphuric  acid.  Further  amalgam  is  added 
in  20-gm.  lots  with  shaking  and  neutralisation  as  before,  until  1  c.c.  of  the 
solution  will  reduce  not  more  than  0-2  c.c.  of  Fehling's  solution. 

The  temperature  throughout  must  not  exceed  20°  C. ;  the  operation  will 
take  about  3  hours,  and  400  gms.  (excess)  of  2-|%  amalgam  will  be  required. 
When  reduction  is  complete,  the  solution  is  separated  from  the  mercury, 
exactly  neutralised  with  10%  sulphuric  acid,  heated  on  a  water  bath  to 
60°,  and  poured  with  stirring  into  1  litre  of  alcohol,  and  the  precipitated 
sodium  sulphate  filtered  off  at  the  pump.  The  filtrate  is  concentrated 
on  a  water  bath  to  about  25  c.cs.,  and  until  crystals  begin  to  separate,  the 

N  2 


180  SYSTEMATIC  ORGANIC  CHEMISTRY 


alcohol  distilling  being  recovered.  The  residual  liquid  is  cooled  to  0°  and 
filtered.  The  precipitated  sodium  sulphate  is  extracted  with  80% 
alcohol  to  recover  any  dulcitol  it  may  contain. 

H2 

CH2OH.(CHOH)4.CHO  >  CH2OH.(CHOH)4CH2OH. 

Yield. — 50%  theoretical  (5  gms.).    Colourless  crystals  ;  sweet  taste  ; 
very  soluble  in  water  ;  M.P.  188°.    (B.,  20,  1091  ;  25,  2564.) 
Peepaeation  108. — Phenyl  Methyl  Carbinol  (1-Phenyl-l-ethanol). 

CH(CH3)(C6H5)(OH).       C8H10O.  122. 

15  gms.  (1  mol.)  of  acetophenone  are  dissolved  in  150  gms.  of  absolute 
alcohol,  and  the  whole  warmed  on  a  water  bath.  15  gms.  (excess)  of  sodium 
wire  are  rapidly  added,  and  when  reaction  has  ceased,  carbon  dioxide  is 
passed  in  until  it  is  no  longer  absorbed.  350  c.cs.  of  water  are  added 
and  the  mixture  evaporated  on  a  water  bath  until  nothing  further  distils, 
the  alcohol  being  recovered.  The  residue  is  extracted  with  ether  and  dried 
over  potassium  carbonate,  the  ether  removed  on  a  water  bath,  and  the 
residue  fractionated  under  reduced  pressure,  the  fraction  97° — 103°  at 
15  mm.  being  retained.    (Cf.  Preparation  18). 

H2 

C6H5CO.CH3   >  C6H5.CHOH.CH3. 

Yield. — 45%  theoretical  (6-5  gms.).  Colourless  liquid  ;  slightly  soluble 
in  water;  B.P.760,  198°;  B.P.40,  118°;  B.P.20,  111°;  B.P.15,  100c. 
(B.,  31,  1003.) 

Peepaeation  109. — Benzhydrol  (Diphenylmethanol). 

HC(C6H5)2(OH).       C13H120.  184. 

10  gms.  (1  mol.)  of  benzophenone  are  dissolved  in  200  c.cs.  of  alcohol, 
and  40  gms.  of  50%  aqueous  caustic  potash  added.  The  mixture  is 
treated  with  100  gms.  of  good  zinc  dust,  and  the  whole  allowed  to  stand 
near  a  water  bath  for  a  week.  After  neutralisation  with  carbon  dioxide, 
it  is  filtered  at  the  pump,  and  the  filtrate  evaporated  until  crystals  separate 
on  cooling  a  sample. 

H2 

(C6H5)2CO   >  (C6H5)2CHOH. 

Yield— 10%  theoretical  (7  gms.).  Colourless  needles  ;  slightly  soluble 
in  water  ;  M.P.  68°.    (J.  pr.,  [2],  33,  184.) 

Reaction  LXIV.  (6)  Reduction  of  Aldehydes  and  Ketones  to  the 
corresponding  Alcohols  by  the  use  of  Acid  Reducing  Agents.  (B.,  37, 
1677.) — Acid  reducing  agents  are  not  widely  used  owing  to  the  danger  of 
forming  pinacones  or  of  complete  reduction  to  the  corresponding  hydro- 
carbon occurring  ;  the  latter  always  takes  place  if  hydriodic  acid  be  used. 
But  in  the  aromatic  series,  especially  with  diketones,  the  milder  acid- 
reducing  agents — zinc  dust  and  sulphuric  acid,  zinc  dust  or  iron  and 
glacial  acetic  acid,  and  stannous  chloride  and  hydrochloric  acid  give  good 
results. 


THE  LINKING  OF  HYDROGEN  TO  CARBON  181 


Preparation  110.— Hydrobenzoin  (1 :  2-Diphenyl-l :  2-ethandiol). 

C6H5.CHOH.CHOH.C6H5.       C14H1402.  214. 

15  gms.  (1  mol.)  of  benzoin  dissolved  in  200  c.cs.  of  alcohol  are  heated  on 
a  water  bath  with  20  gms.  (excess)  of  stannous  chloride  in  50  c.cs.  of  20% 
hydrochloric  acid  for  about  \  hour  and  until  complete  decolonsation  has 
occurred.  The  cooled  liquid  is  filtered  at  the  pump,  and  the  precipitate 
washed  with  water  and  recrystallised  from  glacial  acetic  acid  or  aqueous 
alcohol. 

C6H5.CO.CHOH.C6H5  +  SnCl2  +  2HC1 
=  C6H5.CHOH.CHOH.C6H5  +  SnCl4. 

Yield.—  Almost  theoretical  (15  gms.).    Colourless  leaflets  ;  insoluble  in 
water  ;  M.P.,  134°.    (B.,  37,  1677.) 
Reaction  LXIV.    (c)  Reduction  of  Quinones.    (A.,  27,  268  ;  45,  354  ; 

215,  127  ;  B.,  19,  1467  ;  20,  1854,  2283  ;  21,  1172  ;  40,  390,  924  ;  J.  pr., 
[2],  76,  141 ;  Meyer  and  Jacobson,  Lehrbuch  (ii.),  421).— All  benzqumones 
are  very  readily  reduced  to  the  corresponding  quinols  ;  sulphurous  acid 
being  the  reagent  most  usually  employed.  In  the  reduction  the  greenish 
coloured  quinhydrone  (see  p.  218)  is  intermediately  formed. 


O 


HO 


O 


OH 


2 

H2) 

->  2 

I 

X/ 
II 

0 

Benzquinone. 


■  O 


HO 


OH 
Quinol. 


Quinhydrone. 

Phenylhydrazine  and  hydroxylamine  also  reduce  quinone  to  quinol ; 
they  do  not  react  with  it  as  with  other  oxy-compounds. 

The  anthraquinones  may  be  reduced  to  the  corresponding  "  anthra- 
quinols  "  (hydroxyanthranols)  with  alkaline  sodium  hydrosulphite  ;  this 
reaction  has  a  wide  application  in  the  dye  industry.  These  compounds 
are  difficult  to  isolate  pure,  for  they  rapidly  oxidise  in  air.  The  anthranols 
—  y-monohydroxyanthracenes — however,  are  stable,  and  may  be  obtained 
by  reducing  anthraquinone  with  acid-reducing  agents — tin  and  hydro- 
chloric acid,  zinc  and  glacial  acetic  acid,  copper  or  aluminium,  and 
sulphuric  acid,  etc.  For  the  complete  reduction  of  anthraquinone^  see 
Reaction  LVIII.  (a). 

Preparation  111. — Quinol  (1 :  4-Di-hydroxybenzene). 

C6H4(OH)2[l  :  4].        C6H602.  110. 

10  gms.  (1  mol.)  of  finely  powdered  quinone  are  suspended  in  water, 
and  the  liquid  saturated  with  sulphur  dioxide  until,  after  the  intermediate 
formation  of  quinhydrone,  complete  solution  and  decolorisation  have 
occurred,  the  operation  being  carried  out  in  a  fume  cupboard.  The  liquid 
is  repeatedly  extracted  with  ether  until  nothing  further  is  removed,  the 


182  SYSTEMATIC  ORGANIC  CHEMISTRY 


ether  expelled  on  a  water  bath,  and  the  residue  recrystallised  from  dilute 
sulphurous  acid  with  the  addition  of  animal  charcoal. 

If  preferred,  the  crude  suspension  of  quinone  obtained  from  25  gms. 
of  aniline  (see  p.  229)  may  be  employed,  being  saturated  with  sulphur 
dioxide  until  it  smells  very  strongly  of  the  gas.  After  standing  for  2  hours, 
if  it  still  smells  of  the  gas  the  liquid  is  extracted  with  ether,  as  above.  If 
the  odour  of  the  gas  has  vanished,  the  liquid  must  be  resaturated,  and  so 
on,  until  the  smell  persists  for  the  2  hours. 

H2 

C6H402   >  C6H4(OH)2. 

Yield. — 80%  theoretical  (8  gms.).  Colourless  prisms  ;  soluble  in  ether, 
alcohol,  and  warm  water  ;  sublimes  at  a  gentle  heat ;  M.P.  169°.  (A.,  27, 
268  ;  45,  354  ;  215,  127  ;  B.,  19,  1467  ;  20,  2283.) 

Peepaeation  112. — Anthranol  (y-Mono-hydroxy-anthraquinone). 

CH 

C6H4</|      \C6H4.       C34H10O.  194. 

10  gms.  (1  mol.)  of  anthraquinone  and  30  gms.  (excess)  of  granulated 
zinc  are  refluxed  with  500  c.cs.  of  glacial  acetic  acid,  the  operation  being 
performed  in  a  good  fume  cupboard.  Cone,  hydrochloric  acid,  a  few 
c.cs.  at  a  time,  is  added  until  no  coloration  occurs,  and  hydrogen 
is  continuously  evolved.  After  \  hour  and  when  a  sample  no  longer 
deposits  crystals  on  cooling,  the  whole  is  cooled,  poured  into  dilute 
hydrochloric  acid,  and  the  precipitate  recrystallised  from  glacial  acetic 
acid,  to  wnich  a  little  zinc  dust  and  hydrochloric  acid  have  been  added 
to  prevent  reoxidation. 

Yield. — 80%  theoretical  (14-5  gms.).  Colourless  needles  ;  insoluble 
in  water  ;  M.P.  (decomposition),  170°.    (B.,  20,  1854  ;  D.R.P.,  201542.) 


i 


CHAPTER  XI 


HYDROGEN  TO  CARBON 
OXY  AND  HYDROXY-OXY  COMPOUNDS 

Aldehydes,  Ketones  and  Acids 

The  reductions  in  this  section  are  mostly  those  of  acids  to  aldehydes  ; 
they  are  naturally  few  since  oxygenated  compounds  are  not  usually 
obtained  by  reduction  of  more  highly  oxygenated  substances ;  the 
reverse  process  is  much  more  often  employed. 

Reaction  LXV.  (a)  Reduction  of  Phenolic  Acids  to  the  corresponding 
Aldehydes  by  the  action  of  Sodium  Amalgam  and  Boric  Acid  in  the  presence 
of  a  Primary  Aromatic  Amine.  (B.,  41,  4147.) — This  is  one  of  the  few 
methods  of  reducing  an  acid  to  the  corresponding  aldehyde  in  satisfactory 
yield.  The  presence  of  the  primary  aromatic  base  is  essential  to  protect 
the  aldehyde  ;  it  condenses  with  it  as  formed,  and  inhibits  further  reduc- 
tion to  the  alcohol.  A  weak  acid  such  as  boric  acid  is  used  partly  because 
salt  formation  by  the  base  would  hinder  condensation  and  partly  to  avoid 
hydrolysis  of  the  condensation  product. 

H2(R1NH2)  H20 
OH.R.COOH  >  OH.K.CH  :  NKX  >  OH.R.CHO 

This  method  of  preparing  phenolic  aldehydes  has  the  advantage  over 
Reimer's  (pp.  98, 117)  of  not  giving  a  mixture  of  isomers.  The  yields  also 
are  improved. 

Preparation  113. — Salicyl-aldehyde  (l-Hydroxy-2-benzaldehyde). 

C6H4.(OH).(CHO)[l  :  2],       C7H602.  122. 

20  gms.  (1  mol.)  of  salicylic  acid  dissolved  in  hot  water  are  neutralised 
with  N/1  caustic  soda,  using  phenolphthalein  as  indicator,  and  the  solution 
diluted  to  1  litre  and  boiled.  30  gms.  (excess)  of  j9-toluidine  are  added, 
and  the  whole  cooled  and  mechanically  stirred.  400  gms.  of  sodium 
chloride  and  30  gms.  (excess)  of  boric  acid  are  added  gradually,  and  still 
with  stirring  400  gms.  (excess)  of  2J%  sodium  amalgam  (see  p.  505), 
bhe  solution  being  maintained  faintly  acid  by  the  addition  of  boric  acid 
(about  200  gms.)  from  time  to  time.  The  reaction  is  complete  when  a 
sample,  after  filtration  and  acidification  with  hydrochloric  acid,  gives  no 
precipitate  of  salicylic  acid.  The  condensation  product  of  the  aldehyde 
and  base  is  filtered  at  the  pump,  suspended  in  10%  sulphuric  acid,  and 
distilled  in  steam.  The  aldehyde  distils  and  is  extracted  from  the  dis- 
tillate with  ether.  The  extract  is  dried  over  calcium  chloride,  the  ether 
removed  on  a  water  bath,  and  the  residue  fractionated  between  195°  and 

183 


184  SYSTEMATIC  ORGANIC  CHEMISTEY 


197°.  The  aldehyde  may  also  be  purified  by  means  of  its  bisulphite  com- 
pound (see  Preparation  154). 

C6H4(OH)(COOH)  +  H,  +  (CH3)(C6H4)NH2 
->    C6H4(OH)CH  :  NC6H4CH3  +  2H20 
C6H4(OH)CHO  +  H2N.C6H4.CH3. 

Yield. — 60%  theoretical  (8  gms.).  Colourless  crystals  or  liquid ; 
pungent  odour ;  soluble  in  water  ;  miscible  in  all  proportions  with 
alcohol  and  ether  ;  volatile  in  steam  ;  M.P.  20°  ;  B.P.  196-5°  ;  D1345, 
1-173.    (B,  41,  4147.) 

Reaction  LXV.  (b)  Reduction  of  Lactones  to  the  corresponding 
Hydroxy-aldehydes  by  the  action  of  Sodium  Amalgam  in  faintly  Acid 
Solution.  (A.,  270,  72,  87  ;  272,  200.)— This  is  a  reaction  very  similar  to 
the  previous  one.  It  finds  an  extensive  application  in  the  sugar  group 
for  reducing  the  lactones  of  the  poly-hydroxy  acids  to  the  corresponding 
aldoses.  Combined  with  the  cyanhydrin  reaction  (see  p.  150)  it  forms 
a  means  of  passing  from  one  group  of  sugars  to  the  next  higher  group — 
thus  : 


CH2OH 

I 

CHOH 

I 

CHOH 
I 

CHOH 

(!ho 


CHOH 


HCN 


CH2OH 

CHOH 

I 

CHOH 

I 

CHOH 
CH(OH)CN 


H„0 


CH2OH 

I 

CHOH 

/CH 

/  I 

CHOH 

I 

CHOH 


H, 


CHOH 
I 

CHOH 

CHOH 

I 

CHOH 


CHO 
Preparation 
■  +). 


114.— a-Gluco-heptose  (Hexahydroxy-heptanol  +  + 

CHO 

I 

HCOH 


HCOH 

! 

HOCH 
HCOH 


C7H1407. 


210. 


HCOH 

L  _ 


THE  LINKING  OF  HYDROGEN  TO  CARBON  185 


15  gms.  (1  mol.)  of  the  lactone  of  a~gluco-heptonic  acid  (see  p.  123) 
are  dissolved  in  150  c.cs.  of  water  in  a  thick- walled  500-c.c.  vessel,  and  are 
cooled  in  a  freezing-mixture  to  0°  C.  2  c.cs.  of  10%  sulphuric  acid  are 
added,  and  the  whole  mechanically  agitated,  being  meanwhile  kept 
immersed  in  the  freezing  mixture.  125  gms.  (excess)  of  2-|%  sodium 
amalgam  (see  p.  505)  are  added,  and  at  intervals  further  2-c.c.  lots  of 
10%  sulphuric  acid,  so  that  the  liquid  always  remains  acid.  The  tempera- 
ture must  not  be  allowed  to  rise  above  5°.  In  about  10  minutes  the 
amalgam  will  be  used  up,  a  further  125  gms.  are  added,  and  the  procedure 
of  treating  with  acid  repeated.  The  whole  operation  will  take  about 
40  minutes.  The  solution  is  separated  from  the  mercury  and  any 
unchanged  lactone,  and  converted  to  the  sodium  salt  by  adding  sodium 
hydroxide  until  the  liquid  remains  alkaline  after  standing  for  30  minutes. 
The  solution  is  then  exactly  neutralised,  at  first  with  5%  and  ultimately 
with  N/1  sulphuric  acid,  brought  to  the  boil  with  animal  charcoal  and 
filtered  ;  8  volumes  of  hot  alcohol  are  added  with  constant  stirring,  the 
whole  left  at  room  temperature  for  12  hours,  and  sodium  sulphate  and 
most  of  the  organic  sodium  salts  present  which  are  precipitated  are 
filtered  off  at  the  pump.  The  filtrate  is  slowly  concentrated  until  crystal- 
lisation begins,  is  cooled  and  after  some  hours  filtered  at  the  pump.  The 
precipitate  is  washed  first  with  55%,  then  with  85%,  and  finally  with 
absolute  alcohol. 

/co  CHO 

/     I                 H2  ! 
O     (CH2OH)2   L>  (CHOH)5 

\     |  I 
\CH  CH2°H 

(CHOH)2 

CHOH. 

Yield— 35%  theoretical  (5  gms.).  Colourless  crystals  ;  soluble  in 
water  ;  M.P.  190°  (M.P.  ozazone  195°).    (A.,  270,  72,  87  ;  272,  200.) 

Reaction  LXVI.  (a)  Reduction  of  Unsaturated  Acids  by  means  of 
Sodium  Amalgam  in  Alkaline  Solution.  (A.,  121,  375  ;  137,  237.)— The 
preparation  below  illustrates  an  important  application  of  sodium  amalgam, 
this  substance  being  especially  useful  for  reducing  groups  or  double  bonds 
in  compounds  containing  carboxyl,  as  the  alkali  present  both  keeps  the 
substance  in  solution  and  protects  the  acid  group. 

Preparation  115.— Hydrocinnamic  Acid  (3-Phenyl-propan  Acid). 

C6H5.CH2.CH2.COOH.       C9H10O2.  150. 

20  gms.  (1  mol.)  of  cinnamic  acid  dissolved  in  a  little  more  than  the 
equivalent  amount  of  caustic  soda  (145  c.cs.  of  N-solution)  are  placed  in  a 
stout-walled  vessel  fitted  with  a  mechanical  stirrer  and  350  gms.  (excess) 
of  2J%  sodium  amalgam  (see  p.  505)  are  added  gradually  with  vigorous 
agitation  in  the  course  of  1  hour.  When  no  more  hydrogen  is  evolved, 
the  mercury  is  separated,  washed  with  water,  the  washings  being  added 


186  SYSTEMATIC  ORGANIC  CHEMISTRY 


to  the  rest.  The  liquid  is  acidified  with  an  excess  of  20%  hydrochloric 
acid  ;  on  cooling  an  oil  separates,  which,  on  rubbing  with  a  glass  rod, 
solidifies  ;  it  is  filtered  off  at  the  pump,  dried,  and  recrystallised  from 
petroleum  ether,  or  from  warm  water,  crystallisation  at  a  low  temperature 
being  necessary  owing  to  the  relatively  low  melting  point  of  the  substance. 

C6H5.CH  :  CH.COOH  +  H2  =  C6H5.CH2.CH2.COOH. 

Yield. — 85%  theoretical  (17  gms.).  Colourless  prisms  ;  insoluble  in 
cold,  somewhat  soluble  in  warm  water  ;  soluble  in  alcohol ;  volatile  in 
steam.    M.P.  47°  ;  B.P.  280°.    (A.,  121,  375  ;  137,  237.) 

Reaction  LXVI.  (b)  Reduction  of  Hydroxy  Acids  by  the  action  of 
Hydriodic  Acid.  (A.,  114,  106.) — Hydriodic  acid  is  especially  useful  in 
reducing  groups  or  ethylene  linkages  in  acids  as,  although  a  powerful 
reducing  agent,  it  does  not  readily  attack  the  carboxyl  group.  It  may 
be  used  either  in  a  solvent,  e.g.,  glacial  acetic  acid,  or  more  usually  the 
reaction  is  carried  out  by  heating  to  a  high  temperature  in  a  sealed  tube. 
Red  phosphorus  is  as  usual  added  so  that  it  may  react  with  the  iodine 
freed  in  the  reduction  to  reform  hydriodic  acid  ;  in  this  way  if  sufficient 
phosphorus  be  present  a  small  amount  of  hydriodic  acid  can  reduce  a 
large  quantity  of  substance. 

R1E2C(OH)COOH  +  2HI  =  K^CHCOOH  +  H20  +  I2. 
P  +  31  =  PI3. 
PI3  +  3H20  =  P(OH)3  +  3HI. 

Phosphorous  Acid. 

Preparation  116. — Succinic  Acid  (Butan  diacid). 

COOH.CH2.CH2.COOH.       C4H604.  118. 

10  gms.  (1  mol.)  of  mafic  acid  are  dissolved  in  40  gms.  (excess)  of  57% 
(constant  boiling  mixture)  hydriodic  acid  (see  p.  502)  and  the  solu- 
tion, together  with  3  gms.  of  red  phosphorus,  heated  in  a  sealed  tube 
(see  p.  38)  in  a  tube  furnace  at  130°  for  6  hours.  When  cool,  the  tube 
is  opened  (caution  !  see  p.  41),  the  contents  evaporated  to  dryness  on 
a  water  bath,  and  the  cold  residue  extracted  with  small  quantities  of 
chloroform  until  no  more  free  iodine  is  removed.  The  succinic  acid  is  then 
heated  at  70°  to  remove  all  traces  of  chloroform,  and  recrystallised  from 
hot  water. 

COOH.CHOHCH2.COOH  +  2HI  =  COOH.CH2.CH2.COOH  +  H20  +  I2, 

Yield. — 60%  theoretical  (5  gms.).    Colourless  prisms  ;  soluble  in  water, 
alcohol  and  ether  ;  insoluble  in  chloroform  ;  M.P.  182°.    (A.,  114,  106.) 
Preparation  117. — Diphenyl  Acetic  Acid  (Diphenylethan  acid). 

(C6H5)2CH.COOH.       C14H1202.  212. 

20  gms.  (1  mol.)  of  benzilic  acid  (see  p.  105),  10  gms.  of  57%  hydriodic 
acid  (constant  boiling  acid),  10  gms.  of  red  phosphorus  (excess  of  P  +  HI) 
and  120  gms.  of  glacial  acetic  acid  are  refluxed  in  a  round-bottomed  flask, 
in  a  fume  chamber  for  2  hours.    The  solution  is  filtered  at  the  pump, 


THE  LINKING  OF  HYDROGEN  TO  CARBON  187 


poured  while  still  hot  into  an  excess  of  water,  the  precipitate  filtered  of! 
at  the  pump,  washed  with  water  and  recrystallised  from  alcohol. 

(C6H5)2C(OH)COOH  +  2HI  =  (C6H5)2CHCOOH  +  H20  +  I2. 

Yield. — 80%  theoretical  (14  gms.).  Colourless  crystals  ;  insoluble  in 
cold  alcohol ;  M.P.  46°.    (A.,  275,  84.) 

Reaction  LXVII.  (a)  Ketonic  Hydrolysis  of  Alkyl  Derivatives  of 
Aceto-acetic  Ester.  (A.,  138,  211.) — This  reaction  illustrates  one  of  many 
synthetical  uses  of  aceto-acetic  ester.  When  that  ester  or  its  mono-  or  di- 
alkyl  derivatives  is  boiled  with  dilute  aqueous  or  alcoholic  alkalis  or 
baryta  water,  or  sulphuric  acid,  "  ketonic  hydrolysis  "  occurs,  and  acetone 
or  its  mono-  or  di-substituted  derivatives  are  formed — 


CHgCOCRjR] 


H 


CO 


0 


H 


->    CH3CO.CH.EjKn  +  C02  +  C2H5OH. 

Compounds  such  as  aceto-succinic  ester  and  its  derivatives  which 
contain  the  aceto-acetic  ester  grouping,  also  undergo  this  hydrolysis. 


H— OH 


CH3CO.CH.COOC2H2 
H — O.H 


CH3CO.CH2CH2.COCH3  +  2C02  +  2C2H6OH. 


Peeparation  118. — Methyl-Ethyl  Ketone  (2-Butanon). 

CH3.CO.C2H5.       C4H80.  72. 

20  gms.  (1  mol.)  of  methyl-aceto-acetic  ester  are  refluxed  with 
250  c.cs.  (excess)  of  saturated  baryta  until  the  oily  layer  disappears. 
The  solution  is  then  distilled  on  a  water  bath  to  90°  CL  The  distillate  is 
mechanically  shaken  for  3  hours  with  a  saturated  solution  of  sodium 
bisulphite,  and  the  crystals  which  separate  filtered,  well  dried  and  dis- 
tilled with  an  excess  of  dilute  sulphuric  acid  or  sodium  carbonate  solution 
to  90°.  The  distillate  is  dried  over  calcium  chloride  and  redistilled, 
the  fraction  79° — 82°  being  retained. 

CH3COCH(CH3)COOC2H5  +  H20  =  CH3.COCH2CH3  +  C02  +  C2H5OH. 

Yield. — 70%  theoretical  (7  gms.).  Colourless  mobile  liquid  ;  pleasant 
odour  ;  miscible  with  water  ;  B.P.  81°.    (A.,  138,  211.) 

In  an  exactly  similar  way  acetone  (B.P.  56°)  can  be  prepared  from 
aceto-acetic  ester  (see  p.  143) ;  methyl-propyl  ketone  (B.P.  102°)  from 
monoethyl  acetoacetic  ester  (see  p.  135).  The  higher  ketones  may  be 
purified  by  washing  with  saturated  brine  until  alcohol  is  removed ;  they 
are  then,  after  drying  over  calcium  chloride,  fractionated.  In  all  these 
hydrolyses  dilute  aqueous  or  alcoholic  potash,  or  dilute  sulphuric  acid, 
may  be  used  in  place  of  baryta  water.  The  yields  in  these  preparations 
are  all  of  the  same  order — 70%. 


188  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  119. — Acetonyl  Acetone  (2  :  5-Hexandion). 

CH3COCH2.CH2.COCH3.       C6H10O2.  114. 

20  gms.  (1  mol.)  of  di-aceto-succinic  ester  (see  p.  145)  are  mechanically 
shaken  for  several  days  with  250  c.cs.  (excess)  of  5%  aqueous  caustic  soda, 
and  until  no  di-aceto-succinic  ester  separates  on  acidification  of  a  sample 
with  dilute  hydrochloric  acid.  The  solution  is  then  saturated  with 
potassium  carbonate  and  extracted  with  ether,  the  extract  is  washed  with 
brine  to  remove  alcohol,  dried  over  calcium  chloride,  and  distilled,  the 
fraction  192° — 198°  being  retained. 

CH3COCH.COOC2H5 

I  +  2H20  = 

CH3COCH.COOC2H5 
CH3COCH2.CH2COCH3  +  2C02  +  2C2H5OH. 

Yield. — 70%  theoretical  (6  gms.).  Colourless  liquid  ;  agreeable  odour  ; 
miscible  with  water,  alcohol  and  ether;  M.P.  —9°;  B.P.  194°;  D.  24° 
0-973.    (B.,  18,  58  ;  33,  1217.) 

Reaction  LXVH.  (6)  Acid  Hydrolysis  of  Alkyl  Derivatives  of  Aceto- 
acetic  Ester.  (B.,  19,  227.) — When  acetoacetic  ester  or  its  mono-  or 
di-alkyl  derivatives  are  refluxed  with  concentrated  aqueous  or  alcoholic 
potash,  acid  hydrolysis  occurs  and  2  mols.  of  acetic  acid,  or  1  mol.  of  that 
acid,  and  1  mol.  of  a  mono-  or  di-substituted  derivative  are  obtained. 

CH3CO— CRiKuCOOC.Hg 

->    CH3COOH  +  HCRiRnCOOH. 


HO 


II 


It  is  not  possible  to  perform  the  acid  hydrolysis  without  some  ketonic 
hydrolysis  occurring.  This  reaction  and  the  preceding  one  are  important  in 
many  syntheses  of  aliphatic  ketones  and  acids.  They  might  have  equally 
well  been  included  in  the  decomposition  section  (p.  403)  ;  in  fact 
they  are  often  referred  to  as  the  "  ketonic  "  and  "  acid  "  decomposition 
of  acetoacetic  ester.  The  malonic  ester  synthesis  of  fatty  acids  may  be 
compared  with  the  present  reaction. 

Preparation  120. — Methyl-ethyl  Acetic  Acid  (2-Methyl-butan  acid). 

HC(CH3)(C2H5)COOH.       C5H10O2.  102. 

20  gms.  (1  mol.)  of  methyl  ethyl  aceto-acetic  ester  are  refluxed  for 
4  hours  with  40  gms.  (excess)  of  caustic  potash  dissolved  in  15  gms. 
of  50%  alcohol.  The  mixture  is  poured  into  250  c.cs.  of  water  and 
acidified  after  extraction  with  ether  to  remove  unchanged  ester  and 
methyl-^o-butyl  ketone,  a  by-product  formed  as  in  the  previous  reaction. 
The  acid  which  precipitates  as  an  oil  is  extracted  with  ether,  the  extract 
dried  over  calcium  chloride,  and  distilled,  the  fraction  172° — 178°  being 
retained. 

CH3.CO.C(CH3)(C2H5)COOC2H5  +  2H20 
=  CH3.COOH  +  CH(CH3)(C2H5)COOH  +  C2H5OH. 

Yield. — 60%  theoretical  (11  gms.).  Colourless  liquid  ;  optically  active  ; 
B.P.  175°.    (B.,  19,  227.) 


THE  LINKING  OF  HYDKOGEN  TO  CARBON 


189 


In  an  exactly  similar  way  the  esters  shown  in  the  following  table  yield 
the  corresponding  acids. 

Ester.  Corresponding  Acid.  B.P. 

Acetoacetic  ester  ......  Acetic  acid       .  119° 

Methyl  acetoacetic  ester        .        .  .  Propionic  acid  .  141° 

Ethyl  acetoacetic  ester  .....  Butyric  acid      .  162° 

Dimethyl  acetoacetic  ester     ....  Zsobutyric  acid  .  154° 

Diethyl  acetoacetic  ester        .        .        .       .  isocaproic  acid  .  190° 

The  higher  acids  need  not  be  extracted  from  the  acidified  reaction 
product  with  ether,  but  may  be  separated  directly  as  they  are  only  very 
slightly  soluble  in  water. 


CHAPTER  XII 


hydrogen  to  carbon 
Halogen  Compounds 

Only  two  reactions  are  of  sufficient  importance  to  be  considered  here. 

Reaction  LXVIIL  Simultaneous  reduction  and  Halogenation  of  Poly- 
hydric  Alcohols.  (A.,  138,  364.)— When  polyhydric  alcohols  are  heated 
with  hydriodic  acid,  reduction  of  all  the  hydroxyl  groups  save  one  occurs, 
this  latter  is  replaced  by  iodine  to  form  a  secondary  iodide.  In  this  way, 
e.g.,  dulcitol,  or  any  of  the  hexose  alcohols,  yields  normal  secondary  hexyl 
iodide  ;  this  is  of  importance  in  determining  the  chain  structure  of  the 
sugars.    This  reaction  probably  occurs — 


CH2OH 

CH2I 

HI 

(CHOH)4 

(CHI)4 

CH2OH 

1 

CH2I. 

CH3 

1 

HI 

CHI 

1 

(CH2)3 

I 

CH3. 

The  primary  iodide  is  never  formed  in  such  reactions. 
Preparation  121. — Isopropyl  Iodide  (2-Iodo-propan). 

CH3.CHICH3.       C3H7I.  170. 

70  gms.  (excess)  of  iodine,  45  gms.  (excess)  of  glycerol,  and  30  gms. 
(excess)  of  water  are  placed  in  a  250-c.c.  retort  connected  with  a  condenser 
and  receiver  and  placed  in  a  fume  chamber.  10  gms.  (5  atoms)  of  yellow 
phosphorus  (caution  !)  are  added  gradually  in  small  pieces,  the  phosphorus 
being  cut  under  water,  and  transferred  to  the  retort  with  crucible  tongs. 
The  violent  reaction  which  usually  occurs  on  adding  the  phosphorus  must 
be  allowed  to  subside  before  any  more  is  added.  Should  no  reaction 
take  place  on  adding  the  first  three  pieces  of  phosphorus  the  retort  is 
immersed  in  warm  water  until  interaction  commences.  When  the  addition 
of  the  phosphorus  is  complete  the  retort  is  heated  on  a  wire  gauze  until 
no  further  oily  liquid  distils.  The  distillate  is  replaced  in  the  retort  and 
redistilled,  washed  in  turn  with  10%  caustic  soda,  with  sodium  thio- 

190 


THE  LINKING  OF  HYDROGEN  TO  CARBON  191 


sulphate,  again  with  10%  caustic  soda  and  with  water  ;  it  is  dried  over 
calcium  chloride  for  24  hours  and  fractionated  between  88° — 90°. 


5P  +  151 

=  5PIa. 

5PI3  +  15H20 

=  15HI  +  5P(OH)3, 

CH2OH 

CH2I 

/N  i  t  n  n     i    l  crTJ  T 
\j 11  <J  11  -J-  1  oJtil 

=  5  CHI  4 

-  15H20. 

CH2OH 

CH2I 

CH2I 

CH3 

1 

5  CHI  +  10HI 

=  5  CHI  4 

10I2. 

1 

CH2I 

1 

CH3 

1:2:  3-Tri-iodo  propan  is  probably  formed  as  an  intermediate  compound, 
but  it  is  as  yet  unknown  in  the  free  state. 

Yield—  80%  theoretical  (30  gms.).  Colourless  liquid  ;  insoluble  in 
water  ;  B.P.  89°  ;  D.  J  1-744.    (A.,  138,  364.) 

Reaction  LXIX.  Partial  reduction  of  Tri-halogen  to  Di-halogen  Com- 
pounds. (C.  r.,  145,  810  ;  146,  1282  ;  B.,  52,  212.)— By  a  suitable  choice 
of  the  reaction  conditions  halogen  compounds,  containing  three  halogen 
atoms  linked  to  one  carbon  atom,  may  be  reduced  to  dihalogen  compounds. 
This  is  an  important  method  of  preparing  the  latter  pure  ;  it  is  not  easy 
to  obtain  them  by  halogenation  reactions  owing  to  the  difficulty  of 
stopping  at  the  right  point.  The  success  of  the  reduction  depends  on  the 
reagent  used,  sodium  arsenite,  for  instance,  reduces  iodoform  to  methylene 
iodide  in  95%  yield.  A  somewhat  similar  reaction  is  seen  in  the  simul- 
taneous reduction  and  oxidation  of  chloral  hydrate  to  dichloracetic  acid 
by  the  action  of  potassium  cyanide  or  ferrocyanide. 

C.C13.CH(0H)2  4-  KCN  =  CHCl2.COOH  +  HCN  +  KC1. 

Preparation  122. — Methylene  Iodide  (Di-iodo-methane). 

H 

I 

I— C— H.       CH2I2.  268. 


100  gms.  (1  mol.)  of  iodoform  are  placed  in  a  round-bottomed  flask 
fitted  with  a  mechanical  agitator,  a  reflux  condenser,  a  dropping-funnel, 
and  a  thermometer.  To  these  are  added  50  c.cs.  of  sodium  arsenite  solution 
prepared  from  27-5  gms.  of  arsenious  oxide  (excess),  53  gms.  caustic  soda 
(excess)  and  260  c.cs.  of  water.  Agitation  is  started  and  the  temperature 
is  raised  to  60° — 65°.  The  remainder  of  the  arsenite  solution  is  now 
gradually  added  during  about  30  minutes,  and  the  whole  allowed  to  stand 
for  a  further  hour,  the  temperature  being  maintained  at  60°— 65°  through- 
out. The  mixture  is  cooled  to  40°,  and  filtered  to  remove  mechanical 
impurities  ;  the  filtrate  consists  of  a  clear  water  solution  with  a  pale 
yellow  oil  underneath.    The  oil  is  separated,  dried  over  calcium  chloride 


192  SYSTEMATIC  ORGANIC  CHEMISTEY 

for  24  hours,  and  distilled  under  reduced  pressure,  the  fraction  106° — 107° 
at  70  mms.  being  retained. 

CHI3  +  Na3As03  +  NaOH  =  CH2I2  +  Nal  +  Na3As04. 

Yield. — 95%  theoretical  (65  gms.).  Colourless  oil ;  insoluble  in 
water  ;  B.P.IO60  ;  "  Organic  Syntheses  "  (Adams),  Vol.  I.  (C.  r.,  145, 
810 ;  146,  1282  ;  B.,  52,  212.) 


CHAPTER  XIII 


the  linking  of  oxygen  to  carbon 
Hydroxy  Compounds 

Alcohols  and  Phenols 

This  section  comprises  a  great  number  of  reactions  since,  besides  those 
which  may  be  classed  under  the  heading  of  oxidations— and  such  reactions 
alone  form  a  large  branch  of  practical  organic  chemistry — it  also  includes 
"  hydroxylation  reactions,"  themselves  also  numerous.  Below  is  given 
a  selection  of  the  more  important,  but  it  will  be  understood  that  many 
more  reactions  would  have  to  be  included  before  anything  approaching 
completion  would  be  attained.  They  indicate  for  the  most  part  methods 
of  replacing  various  elements  and  groups  attached  to  carbon  by  the 
hydroxyl  (OH)  group. 

Reaction  LXX.  Oxidation  of  certain  Hydrocarbons.  (B.,  14,  1944  ; 
A.  SpL,  1869,  300  ;  E.P.,  1948  (1869).)— This  reaction  is  confined  in  the 
aliphatic  series  almost  exclusively  to  the  replacement  by  hydroxyl  of  the 
hydrogen  attached  to  tertiary  carbon  atoms.  A  powerful  oxidising 
agent,  e.g.,  chromic  acid  in  glacial  acetic  acid  is  necessary.  In  the 
aromatic  series  the  reaction  is  somewhat  more  easy  to  accomplish  ;  when 
the  sodium  salt  of  anthraquinone-^-monosulphonic  acid,  for  example,  is 
fused  under  pressure  with  caustic  soda  and  a  little  potassium  chlorate, 
replacement  of  both  a  hydrogen  atom  and  the  sulphonic  acid  group  by 
hydroxyl  occurs,  and  alizarin  (a,  /?-dihydroxy  anthraquinone)  is  obtained 

/COx                      NaOH  .CO. 
C6H4(       ■>C6H3S03Na(/3)  >  C6H4<  >C6H2(OH)2[a,/3]. 

Alizarin. 

(See  p.  384.) 

Preparation  123. — Triphenyl  Carbinol  (Triphenyl-methanol). 

(C6H5)3C(OH).       C19H160.  260. 

12  gms.  (1  mol.)  of  triphenylmethane  dissolved  in  60  gms.  of  glacial 
acetic  acid  are  treated  gradually  in  the  warm  with  12  gms.  (excess)  of 
chromic  acid.  Gentle  heating  is  continued  until  a  sample  poured  into 
water  gives  a  precipitate  which  does  not  melt  below  100°  (1 — 2  hours). 
The  whole  is  then  poured  into  water  and  the  precipitate  filtered,  washed 
with  water,  dried  on  a  water  bath,  and  recrystallised  from  benzene. 

(C6H5)3CH  +  O  =  (C6H5)3C(OH). 

Yield. — 85%  theoretical  (11  gms,).    Colourless  crystals  ;   soluble  in 
hot  benzene  and  glacial  acetic  acid  ;  M.P.  158°.    (B.,  14,  1944.) 
s.o.c.  193  o 


194  SYSTEMATIC  ORGANIC  CHEMISTRY 


Reaction  LXXI.  Replacement  of  Halogen  by  Hydroxyl.  (B.,  14,  2394  ;  - 
16,  2954  ;  25,  3290  ;  J.  pr.,  11,  229  ;  A.  Ch.,  [3],  55,  400.)— When  alkyl 
halides  are  refluxed  with  dilute  caustic  alkali  or  alkali  carbonate,  hydroxyla- 
tion  smoothly  occurs.  If  the  halide  be  tertiary  the  replacement  takes 
place  with  great  ease,  warming  with  water  being  sufficient ;  a  secondary 
halide  reacts  less  readily,  but  more  so  than  a  primary.  Aryl  halides 
are  replaced  with  great  difficulty  unless  there  be  present  negative  sub- 
stituents  in  the  ortho-  or  ^ara-positions  when  the  halogen  behaves  as  if  it 
were  attached  to  an  alkyl. 

2C6H3C1(N02)2[1  :  2  :  41  ■+  K2C03  +  H20  = 
2C6H3(OH)(N02)2[l  :  2  :  4]  +  C02  +  2KC1. 

Water  can  always  be  used  to  bring  about  the  hydroxylation  if  the 
heating  be  carried  out  under  pressure.  It  is  to  be  noted  that  this  reaction 
could  also  have  been  discussed  under  the  hydrolysis  of  esters  (p.  234). 

Peepaeation  124. — Benzyl  Alcohol  (Phenyl-methanol). 

C6H5.CH2OH.       C7H80.  108. 

10  gms.  (1  mol.)  of  benzyl  chloride  are  refluxed  with  10  gms.  (excess) 
of  potassium  carbonate  in  100  c.cs.  of  water  until  the  smell  of  benzyl 
chloride  has  disappeared  (6  hours).  The  liquid  is  extracted  with  ether, 
the  extract  dehydrated  by  standing  8  hours  over  anhydrous  potassium 
carbonate,  filtered  into  a  small  distilling  flask,  and  the  ether  removed  on  a 
water  bath.  Distillation  is  continued  with  an  air  condenser  over  wire 
gauze,  the  fraction  200° — 210°  being  collected  separately. 

2C6H5CH2C1  +  K2C03  +  H20  =  2C6H5CH2OH  +  2KC1  +  C02. 

Yield. — 70%  theoretical  (7  gms.).  Colourless  liquid;  aromatic  odour; 
somewhat  soluble  in  water  ;  miscible  in  all  proportions  with  alcohol  and 
ether  ;  B.P.  206-5°  ;  D.  J  1-0628  ;  D.  1544  1-05.    (B.,  25,  3290.) 

In  a  similar  manner,  by  refluxing  ethyl  chloride  with  excess  of  10% 
caustic  soda  and  subsequent  distillation  ethyl  alcohol  is  obtained. 

The  use  of  water  in  the  hydroxylation  of  compounds  containing  a  mobile 
halogen  atom  is  illustrated  in  the  following  two  preparations. 

Peepaeation  125. — m-Chloro-^-hydroxy-benzyl  Alcohol  ( ( (3-chlor-4- 
hydroxy-benzyl)-l)-methanol). 

CH2OH 

C7H702C1.  158-5. 

\/Cl 
OH 

10  gms.  (1  mol.)  of  3-chlor-4-hydroxy-benzyl  chloride  are  refluxed  for 
1  hour  with  100  c.cs.  of  water.  The  cooled  mixture  is  extracted  with 
ether,  the  ether  removed  on  a  water  bath  and  the  oil  which  remains 
scratched  with  a  glass  rod  until  it  crystallises.  The  crystals  are  pressed 
on  a  porous  plate  and  recrystallised  from  benzene. 


THE  LINKING  OF  OXYGEN  TO  CARBON 


195 


C6H3(CH2C1)(C1)(0H)[1  :  3  :  4]  +  H20  = 
C6H3(CH2OH)(Cl)(OH)[l  :  3  :  4]  +  HCL 

Colourless  needles  ;  insoluble  in  water,  soluble  in  hot  benzene  and  in 
ether  ;  M.P.  123°.    (B.,  34,  2459.) 

It  will  be  observed  that  the  nuclear  halogen  atom  in  the  above  com- 
pound is  not  replaced  in  the  reaction. 

Peepaeatton  126. — Glycollic  Acid  (2-Ethanol  Acid). 

CH2(OH)COOH.       C2H403.  76. 

20  gms.  (1  mol.)  of  potassium  chloracetate  or  potassium  bromacetate 
are  dissolved  in  80  c.cs. (excess)  of  water,  and  the  solution  exactly  neutralised, 
with  sodium  carbonate  solution,  and  refluxed  for  16  hours — porcelain 
chips  being  added  to  prevent  bumping.  It  is  cooled  and  concentrated  to 
half  its  bulk  under  reduced  pressure.  The  potassium  halide  which  has 
separated  is  filtered  off,  and  the  nitrate  evaporated  to  dryness  under 
reduced  pressure.  The  residue  is  extracted  in  a  reflux  apparatus  with 
50  c.cs.  of  boiling  acetone  and  the  extract  evaporated  to  dryness  on  a 
bath  kept  at  65°. 

CH2Cl.COOK  +  H20  =  CH2(OH)COOH  +  KC1. 

Yield. — 80%  theoretical  (13  gms.).  Colourless  deliquescent  crystals  ; 
soluble  in  water  and  in  acetone  ;  M.P.  80°  ;  K  =  0-0152.  The  presence 
£>f  the  carboxyl  group  renders  halogen  atoms  attached  to  the  a-carbon 
labile  and  easily  replaceable. 

The  above  compound  can  also  be  prepared  by  boiling  chloracetic  acid 
with  an  aqueous  suspension  of  chalk  (B.,  16,  2954). 

Peepakation  127. — Ethylene  Glycol  (1 :  2-Ethandiol). 

CH2OH.       C2He02.  62. 
By-product :  (1:2:  2-Tribromethan). 

CH2Br        C2H3Br3.  267. 
CHBr2. 

Method  I. — 9-4  gms.  (1  mol.)  of  ethylene  dibromide  (see  p.  332)  are 
refluxed  with  6-9  gms.  (1  mol.)  of  pure  potassium  carbonate  dissolved  in 
50  c.cs.  of  water.  From  the  top  of  the  reflux  condenser  a  glass  tube  is 
led  to  a  couple  of  wash  bottles  containing  bromine.  Some  porcelain  chips 
are  added  to  the  mixture  to  facilitate  ebullition.  When  all  the  oily  drops 
have  disappeared  (8 — 10  hours)  the  same  quantities  of  ethylene  dibromide 
and  potassium  carbonate  are  added  to  the  solution,  and  the  boiling  con- 
tinued as  before.  The  operation  is  prolonged  until  564  gms.  of  ethylene 
dibromide  have  been  decomposed.  After  the  third  addition  of  ethylene 
dibromide,  crystals  of  potassium  bromide  separate  out  on  standing  over- 
night. These,  and  those  which  separate  out  after  each  succeeding  opera- 
tion, are  removed  by  filtration  at  the  pump  before  the  action  is  re- 
started. The  crystals  are  then  washed  with  absolute  alcohol,  the  washings 
being  subsequently  used  for  the  isolation  of  glycol  (see  p.  196).  After 

o  2 


196  SYSTEMATIC  ORGANIC  CHEMISTRY 


decomposition  of  the  ethylene  dibromide  is  complete,  the  solution  of  glycol 
is  heated  on  a  water  bath  at  50°  under  reduced  pressure  in  the  apparatus 
shown  on  p.  27,  so  as  slowly  to  distil  off  the  water.  When  the  distillation 
has  continued  for  some  time,  the  liquid  begins  to  bump  violently,  owing 
to  the  separation  of  potassium  bromide.  The  solution  is  cooled,  the 
crystals  of  potassium  bromide  removed  as  before,  and  the  distillation  con- 
tinued. When  the  solution  becomes  very  viscid,  and  the  temperature  of 
the  vapour  passing  over  begins  to  rise,  the  distillation  is  stopped,  and 
the  residue  is  mixed  with  the  alcohol  used  for  washing  the  potassium 
bromide  crystals,  as  explained  above.  After  standing  for  some  time,  the 
crystals  of  potassium  bromide  which  separate  in  quantity  are  removed 
by  filtration  at  the  pump,  washed  with  absolute  alcohol,  and  the 
combined  alcoholic  extracts  concentrated  by  slow  distillation  as  before 
from  a  flask  fitted  with  a  column.  The  residue  is  treated  with  absolute 
alcohol  which  separates  more  potassium  bromide  ;  this  treatment  is 
repeated,  using  a  mixture  of  alcohol  and  ether,  until  all  the  potassium 
bromide  has  been  removed.  The  solvent  is  removed  by  evaporation  as 
above,  and  the  residual  glycol  twice  fractionated,  at  first  under  reduced 
pressure  (see  B.P.  table  below),  and  finally  at  the  ordinary  pressure. 

CH9Br  CH2.OH 


CELBr 


K2C03  +  H20 


2KBr 


CH..OH 


Yield. — 50%  theoretical  (10  gms.).  Colourless  viscid  liquid  ;  sweet 
taste  ;  blue  in  thick  layers  in  transmitted  light ;  miscible  with  water  in  all 
proportions;  D.  24°  1'134. 

Following  is  a  table  of  boiling  points  at  various  pressures  :— 


Pressure  mms. 
764-5 
760-0 
544-0 
357-0 
101-0 
83-0 
44-0 


B.P.0 
197— 
197 
186-5 
173 
143-8 
136-7 
122-5 


197-5  corrected. 


Isolation  of  By-product.  —  During  the  reaction,  vinyl  bromide 
(CH2  :  CHBr)  is  formed.  It  volatilises  and  is  absorbed  by  the  bromine 
in  the  wash  bottles.  The  product  is  washed  with  dilute  caustic  soda 
until  excess  bromine  is  removed ;  on  fractionating,  tribromethane  is 
obtained  (B.P.  187°). 


CH2Br 

I 

CH2Br 
CH2 

ji 

CHBr 


CH. 


CHBr 


HBr. 


Br, 


CHBr2. 


(J.  C.  S.,  69,  176  ;  J.  pr.,  11,  229  ;  A.,  192,  257  ;  C,  (1907),  1,  1314.) 
The  above  method  is  necessary  where  a  good  yield  of  glycol  is  required. 


THE  LINKING  OF  OXYGEN  TO  CARBON 


197 


If  yield  be  not  a  pressing  consideration,  the  process  may  be  shortened  by 
refluxing  all  the  materials  together  from  the  beginning,  evaporating 
at  80°  under  reduced  pressure  until  little  more  distils ;  extracting  the 
residue  twice  with  absolute  alcohol ;  removing  the  alcohol  under  reduced 
pressure  and  fractionating  the  product. 

Both  these  methods  suffer  from  the  difficulty  of  separating  glycol  from 
a  large  excess  of  water  without  loss.  There  is,  however,  a  second  method 
available  for  replacing  halogen  by  hydroxyl.  It  consists  in  preparing  an 
ester  of  the  desired  alcohol  by  heating  the  halide  with  certain  salts — silver, 
potassium,  or  sodium  acetates — and  saponifying  the  ester  so  formed. 

CH2Br  CH2.OOCCH3 
I  +  2CH3COOK  =  j  +  2KBr 

CH2Br  CH2.OOCCH3. 

For  saponification,  the  ester  is  usually  treated  with  hydrochloric  acid 
dissolved  in  anhydrous  methyl  alcohol. 

CH2.OOC.CH3  CH2OH 

j  +  2HC1  =  I  +  2CH3COCJ. 

CH2.OOC.CH3  CH2OH 

The  acetyl  chloride  reacts  with  the  methyl  alcohol  forming  methyl 
acetate  and  a  fresh  quantity  of  hydrochloric  acid. 

CH3COCl  +  CH3OH  =  CH3COOCH3  +  HC1. 

This  method  has  a  wide  application,  but  it  is  especially  useful  for  the 
preparation  of  glycol. 

Method  II. — 200  gms.  of  pure  potassium  acetate  are  fused  in  a  shallow 
dish,  as  described  on  p.  506,  except  that,  unlike  sodium  acetate,  the 
crystals  contain  no  water  of  crystallisation,  and  only  melt  once.  The 
solidified  salt  is  finely  powdered,  and  while  still  warm,  placed  in  a 
desiccator. 

60  gms.  (1  mol.)  of  ethylene  dibromide  (see  p.  332),  20  gms.  (excess) 
of  glacial  acetic  acid,  and  60  gms.  (excess)  of  freshly  fused,  finely  powdered 
potassium  acetate  are  refluxed  in  a  500-c.c.  flask  for  2  hours,  and  the 
reaction  product  distilled,  using  a  condenser.  The  distillate  is  again 
treated  with  60  gms.  (1  mol.)  of  ethylene  dibromide,  and  80  gms.  (excess) 
of  freshly  fused,  finely  powdered  potassium  acetate,  refluxed  for  3  hours 
as  before,  and  again  distilled,  using  a  good  fractionating'  column  (see 
p.  21),  the  fractions  (1)  140°,  (2)  140°— 175°,  (3)  above  175°,  being 
collected  separately.  The  last  two  fractions  are  redistilled,  the  fraction 
180° — 190°  being  retained.  The  portion  under  180°  is  again  treated  with 
80  gms.  of  potassium  acetate,  refluxed  and  distilled  as  before.  The  total 
yield  of  glycol  diacetate  is  about  90%  theoretical  (88  gms.).  It  boils  at 
180°. 

40  gms.  (excess)  of  pure  anhydrous  methyl  alcohol  (see  p.  206)  are 
cooled  in  water,  and  gaseous  hydrogen  chloride  (see  p.  502)  led  in  until 
an  increase  in  weight  of  1  gm.  has  been- obtained.  Should  a  greater 
increase  be  found,  the  required  2J%  solution  is  obtained  by  adding  the 
requisite  quantity  of  pure  anhydrous  methyl  alcohol.    The  41  gms.  of 


198  SYSTEMATIC  ORGANIC  CHEMISTRY 


2-5%  alcoholic  hydrogen  chloride  is  refluxed  with  50  gms.  (1  mol.)  of  glycol 
diacetate  on  a  water  bath  for  30  minutes,  and  the  reaction  mixture 
immediately  distilled  from  the  same  bath.  Methyl  alcohol  and  methyl 
acetate  are  thus  removed,  the  residue  consisting  of  glycol  and  a  small 
quantity  of  its  acetate,  two  substances  the  boiling  points  of  which  lie  close 
together.  They  are  separated  by  extraction  with  an  equal  volume  of  dry 
ether,  glycol  remaining  undissolved.  It  is  removed  and  fractionated,  the 
temperature  being  slowly  raised  to  100°C.  The  fraction  192° — 198°  is 
redistilled. 

CH2Br  CH,.O.COCH3 
CH2Br  +  2CH8COOK  =  CH;o.COCH3+  2KBr' 
CH2OCOCH3  CH2OH 

I  +  2HC1  +  2CH3OH  =  I  +  2CH3COOCH3  +  2HC1. 

CH2OCOCH3  CH2OH 

Yield. — 85%  theoretical  (18  gms.)  on  the  glycol  diacetate  taken  ;  75% 
theoretical  on  the  ethylene  dibromide  originally  taken  (24  per  10  of 
ethylene  dibromide).    (Cf.  yield  by  Method  I.    See  p.  196.) 

(Gattermann,  "  Practical  Methods  of  Organic  Chemistry,"  p.  196,  Third 
American  Edition.) 

The  next  preparation  illustrates  the  activating  effect  of  aromatic  nitro 
groups  on  nuclear  halogen  atoms  in  the  0-  and  ^-positions. 

Prepaeation  128. — 2-4-Dinitrophenol  (2-4-Dinitro-l-hydroxy-benzene). 

OH.C6H3(N02)2[l  :  2  :  4].        C6H405N2.  184. 

10  gms.  (1  mol.)  of  chloro-di-nitro-benzene  [1  :  2  :  4]  are  refluxed  with 
15  gms.  (excess)  of  anhydrous  sodium  carbonate  and  150  c.cs.  of  water  until 
solution  has  occurred,  cooled  and  acidified  with  dilute  hydrochloric  acid  ; 
the  precipitate  is  filtered,  washed,  and  dried  on  a  porous  plate. 

2C1.C6H3(N02)2[1  :  2  :  4]  +  Na2C03  +  H20  = 
20H.C6H3(N02)2[1  :  2  :  4]  +  2NaCl  +  C02. 

Yield. — 90%  theoretical  (8  gms.).  Colourless  crystals  ;  insoluble  in 
water  ;  M.P.  114°.    (Z.  Ch.  (1870),  232.) 

Reaction  LXXIL  Replacement  of  the  Diazo  Group  by  Hydroxyl.  (B., 
22,  335  ;  23,  3705  ;  24,  1960  ;  J.  pr.,  14,  451  ;  A.,  137,  39  ;  D.R.P., 
167211.) — -This  is  a  reaction  of  great  importance  in  the  aromatic  series, 
both  in  the  laboratory  and  on  a  manufacturing  scale.  When  diazonium 
salts,  especially  the  sulphate,  are  boiled  with  water  or  acids,  nitrogen  is 
evolved,  and  the  phenol  corresponding  to  the  diazonium  compound  is 
formed.  It  is  not  necessary  to  isolate  the  diazonium  salt,  the  solution 
prepared  in  the  usual  way  from  the  amine  is  boiled  or  slowly  added  to 
boiling  dilute  sulphuric  acid,  or  an  aqueous  solution  of  sodium  nitrite  may 
be  added  to  a  boiling  solution  of  the  amine  in  dilute  sulphuric  acid.  The 
use  of  the  diazonium  nitrate  is  to  be  avoided,  as  simultaneous  nitration 
usually  occurs.  The  reaction  can  be  applied  to  substituted  amines, 
amino-acids,  amino-halogen  compounds,  etc.,  but  the  yields  are  often  poor, 
especially  with  the  amino-phenols  ;  they  may  be  improved  to  some  extent 


THE  LINKING  OF  OXYGEN  TO  CARBON  199 


by  the  use  of  copper  sulphate  solution.  Although  the  method  is  of 
practical  importance  only  in  the  aromatic  series,  since  aliphatic  diazo-com- 
pounds  are  not  formed  except  at  very  low  temperatures,  yet  aliphatic 
hydroxy  compounds  are  readily  obtained  by  the  action  of  aqueous  sodium 
nitrite  solution  on  acid  solutions  of  the  primary  amines.  This  reaction 
should  be  compared  with  the  formation  of  ethers  as  a  by-product  in  the 
reduction  of  diazo  compounds  with  alcohol  (Reaction,  p.  369). 

C6H5.N2.S04H  +  H20  =  C6H5OH  +  N2  +  H2S04. 

Preparation  129. — Phenol  (Hydroxybenzene). 

C6H5.OH.       C6H60.  94. 

20  gms.  (1  mol.)  of  freshly-distilled  aniline  are  dissolved  by  gentle 
warming  in  150  gms.  of  30%  sulphuric  acid,  and  the  cooled  liquid  treated 
with  a  20%  solution  of  sodium  nitrite  until  a  sample  colours  starch-iodide 
paper  (see  p.  501)  ;  some  16  gms.  of  NaN02  will  be  required.  The 
whole  is  kept  at  50°  for  an  hour,  steam  distilled  until  no  more  phenol 
distils  (this  is  shown  by  a  sample  of  the  distillate  giving  no  precipitate 
with  bromine  water),  the  distillate  is  saturated  with  salt,  extracted  several 
times  with  ether  until  nothing  more  is  removed,  and  the  extract  dried 
for  24  hours  over  fused  sodium  sulphate.  The  ether  is  removed  on  a 
water  bath  and  the  residue  distilled,  the  fraction  175° — 185°  being  retained. 

H2S04  +  NaNOo  H20 
C6H5NH2  >  C6H5.N2.S04H   >  C6H5OH. 

Yield. — 35%  theoretical  (7  gms.).  Colourless  needles  ;  characteristic 
odour  ;  somewhat  soluble  in  water  ;  soluble  in  alcohol  and  ether  ;  M.P. 
42°  ;  B.P.  182°.    (B.,  23,  3705  ;  A.,  137,  39  ;  J.  pr.,  14,  451.) 

If  the  residue  in  the  flask  after  the  steam  distillation  be  filtered  hot, 
and  cooled,  crystals  of  j9-hydroxy-di-phenyl  separate.  It  is  formed  by 
the  coupling  of  a  portion  of  the  phenol  first  formed  with  undecomposed 
diazo  compound. 

C6H5.N2.S04H  +  H.C6H4OH  =  C6H4.CeH3OH  +  H2S04  +  N2. 

(Cf.  p.  369.)  _ 

The  yield  is  low  owing  to  the  heating  with  the  mineral  acid  tending 
to  cause  resinification  of  the  phenol.  It  has  been  suggested  to  avoid  this 
to  heat  with  a  weak  acid,  e.g.,  boric  acid,  but  no  great  improvement  in 
the  yield  is  obtained. 

In  an  exactly  similar  manner  from  20  gms.  of  o-  m-  or  ;p-toluidme,  the 
o-,  m-,  or  j?-cresols  respectively  are  prepared  (see  also  p.  369) ;  for 
these  it  is  better  to  use  only  10%  sulphuric  acid,  a  quantity  being  taken 
equivalent  to  the  30%  acid  employed  above.  The  yields  are  of  the  order 
of  50%  (12-5  gms.). 

The  melting  and  boiling  points  of  the  cresols  are  : 

M.P.  BP. 
o-Cresol .        .        .        .        31°  .  191° 

m-Cresol.        ...        —  .  202° 

^-Cresol.     '  .        .        .        36°  .        .  202° 


200  SYSTEMATIC  ORGANIC  CHEMISTRY 


The  method  is  often  important  in  the  preparation  of  hydroxy  derivatives 
of  compounds  the  groups  in  which  render  them  difficult  to  prepare  by 
more  direct  means.  m-Hydroxybenzoic  acid  is  such  a  compound.  It 
is  obtained  by  nitration  of  benzoic  acid  followed  by  reduction  to 
m-amino  benzoic  acid  and  application  of  the  present  reaction  (see  below). 

Peepaeation  130. — m-Hydroxybenzoic  Acid  (l-Hydroxy-3-carboxy- 
benzene). 

C6H4(OH)(COOH)[l  :  3].       C7H603.  138. 

10  gms.  (1  mol.)  of  m-amino  benzoic  acid  hydrochloride  are  dissolved 
in  100  c.cs.  of  water  (or  8  gms.  of  the  free  acid  are  dissolved  in  200  c.cs. 
of  2%  hydrochloric  acid)  and  a  30%  aqueous  solution  of  5  gms.  (excess) 
of  sodium  nitrite  slowly  added.  The  whole  is  warmed  until  nitrogen 
ceases  to  be  evolved,  filtered  at  the  pump  and  evaporated  until,  on 
cooling,  crude  m-hydroxybenzoic  acid  separates  as  a  brown  mass.  It  is 
purified  by  recrystallisation  from  water  with  addition  of  animal  charcoal. 

HN02 

C6H4(NH2)(COOH)[l  :  3]  -   >  C6H4(OH)(COOH)[l  :  3]. 

Yield. — 60%  theoretical  (7  gms.).  Colourless  crystals  ;  soluble  in  hot 
water  ;  M.P.  200°.    (A.,  91,  189.) 

Di-amino  compounds  can  also  be  made  to  yield  di-hydroxy  compounds 
in  this  way. 

Peepaeation  131. — ^-^-Dihydroxy-diphenyl  (4  :  4/-Dihydroxy-l :  V- 
diphenyl). 

[4jOH.C6H4.C6H4.OHt4'].       C12H10O2.  186. 

50  gms.  (1  mol.)  of  benzidine  (see  p.  356)  are  dissolved  in  900  c.cs. 
(2  mols.)  of  2%  hydrochloric  acid,  and  5  litres  (excess)  of  5%  sulphuric 
acid  added.  The  solution  is  diazotised,  as  described  on  p.  366,  with  20% 
aqueous  sodium  nitrite.  About  40  gms.  of  sodium  nitrite  will  be 
required.  Steam  is  passed  into  the  solution  for  30  minutes,  and  until  a 
sample  gives  no  precipitate  with  an  alkaline  solution  of  phenol.  The 
diphenyl  derivative  crystallises  on  cooling  the  solution,  which  is  first 
filtered  hot. 

HN02  +  H2S04 

[4]NH2.C6H4.C6H4.NH2[4']  >  [4]OH.C6H4.C6H4OH.[4']. 

Yield. — 75%  theoretical  (37  gms.).  Colourless  needles  ;  soluble  in  hot 
water  ;  M.P.  272°.    (B.,  22,  335.) 

The  next  preparation  illustrates  the  use  of  copper  sulphate  solution. 
Peepaeation  132. — Quinol  (1 :  4-Dihydroxybenzene). 

C6H4(OH)2[l  :  4].        C6H602.  110. 

30  gms.  (1  mol.)  of  j9-aminophenol  are  diazotised,  as  described  on  p.  365, 
and  the  diazo-solution  slowly  added  to  400  gms.  of  a  boiling  25%  copper 
sulphate  solution.  When  the  evolution  of  nitrogen  ceases  the  solution  is 
cooled  and  extracted  with  ether  until  nothing  further  is  removed.  The 
ether  is  evaporated  on  a  water  bath,  and  the  residue  recrystallised  from 
dilute  sulphuric  acid  with  the  addition  of  a  little  animal  charcoal. 


THE  LINKING  OF  OXYGEN  TO  CARBON 


201 


HN02 

C6Hd(OH)(NH2)[l  :  4]  -   >  C6H4(OH)2[l  :  4j. 

Yield. — 30%  theoretical  (9  gms.).  Colourless  prisms  ;  soluble  in  hot 
water,  in  ether,  and  in  alcohol ;  M.P.  169°  ;  sublimes  at  a  moderate  heat. 
(D.R.P.,  167211.) 

o-,  m-  and  j9-cresols  (see  p.  199)  are  obtained  from  the  corresponding 
toluidines  in  an  exactly  similar  way. 

Catechol  (o-dihydroxybenzene,  M.P.  104°  ;  B.P.  245°)  is  prepared  in 
the  same  manner  from  o-aminophenol,  a  10%  solution  of  copper  sulphate 
being  employed.  Below  is  illustrated  the  effect  of  boiling  a  diazonium 
nitrate  with  water  (p.  369). 

Preparation  133. — m-Nitro-^-Hydroxy  Toluene  (l-Methyl-4-hydroxy- 
3-nitrobenzene). 

C6H3(CH3)(OH)(N02)[l  :  4  :  3J.  C7H703N.  153. 
50  gms.  (1  mol.)  of  finely  powdered  ^>-toluidine  are  dissolved  in  500  gms. 
(excess)  of  warm  10%  nitric  acid  (D  =  1-06),  and  the  solution  diazotised 
at  0°,  as  described  on  p.  366,  a  30%  aqueous  solution  of  30  gms.  of  sodium 
nitrite  being  added  until  the  solution  colours  starch  iodide  paper  ;  on  no 
account  must  the  temperature  rise  above  8°.  After  standing  for  3  hours 
at  0°,  50  c.cs.  of  the  solution  are  slowly  heated  in  a  litre  round  flask  in  an 
oil  bath  under  a  long  reflux  condenser  until  ebullition  occurs  and  inter- 
action commences.  When  the  reaction  is  complete  the  remainder  of  the 
diazo-solution  is  slowly  added,  then  the  boiling  is  continued  for  10  minutes, 
and  the  solution  steam  distilled  until  no  further  oil  comes  over.  The 
solid  nitro-cresol  is  filtered  from  the  distillate,  well  washed  with  water, 
and  purified  by  precipitation  from  an  alkaline  solution  of  its  sodium  salt, 
using  dilute  hydrochloric  acid. 

HN02 

C6H4(CH3)(NH2)[1  :  4]  >  C6H3(CH3)(OH)(N02)[l  :  4  :  3]. 

HN03 

Yield. — 60%  theoretical  (40  gms.).  Yellowish  crystals  ;  insoluble  in 
water  ;  M.P.  36-5°.    (B.,  24,  1960.) 

Reaction  L XXIII.  Direct  Replacement  of  the  Aromatic  Amino-group  by 
Hydroxyl.  (B.,  7,  77,  809;  D.K.P.,  109102.)— The  simple  primary 
amino  groups  in  the  benzene  series  are  not  easily  replaced  directly  by 
hydroxyl  unless  an  activating  group  (e.g.,  N02)  be  present  in  the  o-  or 
^-positions.  a-Naphthols,  however,  are  readily  obtained  by  heating 
a-naphthylamine  derivatives  with  fairly  concentrated  acid  under  pressure. 
C10H7NH2  +  H20  =  C10H7OH  +  NH3. 

(This  reaction  can  be  reversed,  see  p.  295.) 

It  can  be  accomplished  more  readily  by  heating  with  sodium  bisulphite 
solution,  an  unstable  naphthol-sulphite  being  an  intermediate  product, 
^-compounds  also  react. 

C10N7NH2  +  H2S03  =  C10H7O.SO2H  +  NH3. 
C10H7O.SO2H  4-  H20  =  C10H7OH  +  H20  +  S02. 

This  reaction  is  of  technical  importance,  being  applied  to  the  prepara- 
tion of  some  hydroxy-sulphonic  acids. 


202  SYSTEMATIC  ORGANIC  CHEMISTRY 


With  ^-nitroso-secondary  and  tertiary  bases  the  alkyl  amino  group  can 
readily  be  replaced  by  boiling  with  dilute  alkali.  This  method,  too,  is 
illustrated  below. 

Preparation  134. — cc-Naphthol  (1-Hydroxy-naphthalene). 

OH 

|      |      |       C10H8O.  144. 

150  gms.  (1  mol.)  of  a-naphthylamine  (see  p.  352)  are  heated,  with 
120  gms.  (excess)  of  cone,  sulphuric  acid  and  1  litre  of  water,  to  200°  for 
8  hours  at  14  atmospheres  in  an  enamelled  autoclave  (see  p.  42),  fitted 
with  a  stirrer.  On  cooling,  the  autoclave  is  opened  and  a-naphthol  filtered 
off,  washed,  and  recrystallised  from  water,  or  distilled  preferably  under 
reduced  pressure. 

NH2  OH 


Yield. — 95%  theoretical  (140  gms.).  Colourless  crystals  ;  character- 
istic odour  ;  sparingly  soluble  in  water  ;  M.P.  94°  ;  B.P.  280°  ;  is  an 
important  intermediate  for  dyestuffs.    (D.R.P.,  76545.) 

Prepaeation  135.— Nevile  and  Winther's  Acid  (l-Hydroxy-4-Naphtha- 
lene-sulphonic  Acid). 

OH 


C10H8O4S.  224. 


SO.H-. 

100  gms.  (1  mol.)  of  naphthionic  acid  (100%)  (or  the  equivalent  of 
sodium  naphthionate),  dissolved  in  200  c.cs.  of  water  are  refluxed  for  24 
hours  with  600  gms.  (excess)  of  sodium  bisulphite  solution  (25%  S02). 
30%  caustic  soda  solution  is  added  until  the  solution  is  alkaline  to 
phenolphthalein,  and  the  whole  boiled  until  no  more  ammonia  is  evolved. 
Hydrochloric  acid  is  then  added  until  the  product  is  permanently  acid. 
The  Nevile  and  Winther's  acid  crystallises  on  cooling.  It  is  separated 
from  unchanged  naphthionic  acid  by  recrystallisation  from  warm  water. 
It  may  be  obtained  as  its  sodium  salt  by  neutralising  the  warm  solution 
with  caustic  soda,  and  saturating  with  common  salt. 


XI 1 2  OH 


SO3H  S03H. 

Yield. — 80%  theoretical  (80  gms.).  Colourless  crystals  ;  soluble  in 
hot  water  ;  decomposes  on  heating  ;  important  intermediate  for  azo 
dyestuffs.    (B.,  24,  3157  ;  27,  3458  ;  A.,  273,  102  ;  D.R.P.,  109102.) 


THE  LINKING  OF  OXYGEN  TO  CARBON 


203 


Preparation  136. — ^>-Nitroso-Phenol  (l-Hydroxy-4-nitroso-benzene). 

C6H4(OH)(NO)[l  :  4].       C6H502N.  123. 

5  gms.  (1  mol.)  of  ^-nitroso-di-methylaniline  hydrochloride  (see  p.  278) 
are  added  gradually  to  250  gms.  (excess)  of  boiling  2J%  caustic  soda 
solution  in  a  flask  fitted  with  a  reflux  condenser,  the  free  base  which 
separates  as  an  oil,  being  allowed  each  time  to  dissolve  before  the  next 
addition.  The  boiling  is  continued  after  complete  addition  until  the 
solution  has  become  reddish-yellow.  When  cold,  the  liquid  is  acidified 
and  extracted  with  ether,  and  the  latter  removed  on  a  water  bath.  The 
residual  nitroso-phenol  is  redissolved  in  a  little  boiling  water,  and  after 
filtration  and  cooling  it  is  again  extracted  with  ether  and  recovered  by 
evaporation  of  the  ether. 

NO.C6H4.N(CH3)2ri  :  4]  +  H20  =  NO.C6H4OH  +  NH(CH3)2. 
NOC6H4OH  ^ZZ^  HON.C6H4 :  0. 

Yield. — 90%  theoretical  (2-5  gms.).  Colourless  rhombic  crystals  ; 
soluble  in  water,  and  in  ether  ;  M.P.  125°.    (B.,  7,  809.) 

This  reaction  is  frequently  applied  to  the  preparation  of  dialkylamines. 
The  dimethylamine  evolved  in  the  above  reaction  may  be  absorbed  by 
leading  through  hydrochloric  acid  ;  from  the  latter  solution  the  hydro- 
chloride is  obtained  by  evaporation.  ^>-Nitroso-phenol,  it  is  to  be  noted, 
is  tautomeric,  in  some  reactions  behaving  as  quinone  monoxime. 

Reaction  LXXIV.  Action  of  Mineral  Acids  on  Phenylhydroxylamine. 
(B.,  26,  1844,  2810  ;  27,  1927  ;  20,  3040.)— In  the  presence  of  mineral 
acids  phenylhydroxylamine  undergoes  rearrangement  to  form  p-amino- 
phenol. 

C6H5NH.OH  ->  OH.C6H4NH2. 

This  isomerisation  explains  the  course  of  the  electrolytic  reduction 
of  aromatic  nitro  compounds  (see  p.  392)  also  the  oxidation  of  aniline 
to  quinone  (see  p.  229). 

Preparation  137. — £>-Amino-phenol  ( l-Hydroxy-4- amino -benzene ) . 

CeH4(OH)(NH2)[l  :  4].  ->  C6H7ON.  109. 

5  gms.  (1  mol.)  of  phenylhydroxylamine  (see  p.  203)  are  slowly  added 
to  100  c.cs.  of  50%  sulphuric  acid,  cooled  in  a  freezing  mixture,  500  c.cs. 
of  water  poured  in,  and  the  whole  boiled  until  a  sample,  tested  with 
chromic  acid  solution,  gives  a  smell  of  quinone  and  no  smell  of  nitro- 
benzene. The  liquid  is  neutralised  with  sodium  bicarbonate,  saturated 
with  common  salt,  and  extracted  with  ether.  The  ether  is  removed  by 
evaporation,  and  the  residue  washed  with  cold  water  and  dissolved  in 
hot  water.  The  solution  is  filtered  hot,  and  cooled,  and  the  ^>-amino- 
phenol  again  extracted  with  ether. 

C6H5NHOH  ->  OH.C6H4.NH2. 

Yield. — Almost  theoretical  (5  gms.).  Colourless  crystals  ;  somewhat 
soluble  in  water  ;  M.P.  185°.    (B.,  26,  1844,  2810  ;  27,  1927  ;  29,  3040.) 

Reaction  LXXV. — Fusion  of  Aromatic  Sulphonic  Acids  with  Caustic 
Alkalis.   (Z.  Ch.  (1876),  3,  299  ;  J.  pr.,  [2],  17,  394 ;  20,  300.)— This  method 


204 


SYSTEMATIC  ORGANIC  CHEMISTRY 


is  of  technical  importance  as  it  is  employed  to  prepare  various  phenols  and 
naphthols  from  the  parent  hydrocarbons  via  the  corresponding  sulphonic 
acids  ;  these  phenols  and  naphthols  are  much  used  as  intermediates  in 
the  dye  industry.  The  method  is  also  employed  in  the  laboratory,  but 
only  as  a  preparative  method ;  it  cannot  easily  be  applied  to  determine 
structure,  owing  to  rearrangement  being  liable  to  occur  at  the  elevated 
temperatures  used.  Caustic  potash  is  more  convenient  than  soda,  as 
simultaneous  interaction  with  atmospheric  oxygen  is  then  less  liable  to 
occur,  and  also  since  it  yields  generally  a  more  easily  fusible  mixture. 
A  suitable  apparatus  for  laboratory  fusions  is  shown  in  Fig.  50. 
Preparation  138. — Phenol  (Hydroxybenzene). 


C«HsOH. 


94. 


35  gms.  (excess)  of  caustic  potash  are  warmed  with  5  c.cs.  of  water  in 
an  iron  or  nickel  basin  (for  another  suitable  reaction  vessel,  see  below). 
20  gms.  (1  mol.)  of  finely  powdered  potassium  benzene  sulphonate  are 
added,  and  stirred  in  with  a  thermometer,  protected  by  a  glass  or  iron 
tube  (Fig.  50).  The  temperature  is  brought  to  250°,  and  kept  at 
this  point  for  1  hour  :  it  must  not  be  allowed  to  exceed  it.  The  cold 
melt  is  dissolved  in  the  minimum  quantity  of  water,  and  the  solution 
carefully  acidified  under  good  cooling  with  cone,  hydrochloric  acid.  It 
is  repeatedly  extracted  with  ether,  until  nothing  further  is  removed,  the 
extract  is  dried  for  24  hours  over  anhydrous  sodium  sulphate,  the  ether 
removed  on  a  water  bath,  and  the  residue  fractionated  at  175° — 185°. 


K2S03  - 
C6H5OH  +  KC1. 


H,0. 


C6H5OK  +  HC1 

Yield. — 70%  theoretical  (65  gms.).  Colourless  needles  ;  characteristic 
odour  ;  somewhat  soluble  in  water  :  soluble  in  alcohol  and  ether  :  M.P. 
42°  ;  B.P.  182s.    (Z.  Ch.  (1867)  3,  299  ;  J.  pr.,  [2],  17,  394  :  20,  300.) 

Preparation  139. — /3-Naphthol  (2-Hydroxy-naphthaiene). 


/\/\OH 


C10H80. 


144. 


200  gms.  (excess)  of  solid  caustic  soda  free  from 
chlorate,  and  60  c.cs.  water  are  placed  in  a  fusion-pot 
(Fig.  50),  which  consists  of  a  glue-pot  of  the  ordinary 
type,  the  outer  vessel  containing  a  lead  alloy.  The 
thermometer  is  placed  inside  the  iron  tube  containing 
a  little  mercury  at  the  bottom,  and  this  tube  is  used 
as  stirrer.  The  pot  is  heated  until  the  temperature  is 
270°.  300  gms.  of  dry  powdered  sodium  /3-naphthalene 
sulphonate  are  then  gradually  added,  the  temperature 
being  allowed  to  rise  to  290'  when  half  of  the  salt  has 
been  added,  to  300c  when  three-quarters  have  been  added,  and  to  305° 
when  all  has  been  added,  and  finally  to  318c — but  no  higher  for  15 
minutes.     The  melt  after  cooling  somewhat,  is  poured  into  2  litres  of 


Fig.  50. 


THE  LINKING  OF  OXYGEN  TO  CARBON 


205 


water  with  continual  stirring  (caution!).  The  solution  is  then  boiled  and 
carefully  neutralised  with  50%  sulphuric  acid,  an  indicator  being  used. 
The  solution  is  then  filtered  hot,  and  the  ^-naphthol  precipitated  by 
adding  50%  sulphuric  acid  to  the  filtrate  until  strongly  acid.  It  is  then 
filtered  off,  washed  with  water  and  dried,  and  may  be  recrystallised  from 
hot  water. 

C10H7SO3Na  ->  C10H7ONa  ->  C10H7OH. 

Yield. — 70%  theoretical  (130  gms.).  Colourless  crystals  with  charac- 
teristic odour ;  M.P.  122°  ;  B.P.  286°.  Important  intermediate  for 
dyestuffs. 

a-Naphthol  (M.P.  94°  ;  B.P.  280°)  is  prepared  from  sodium  a-naphtha- 
lene-sulphonate  in  an  exactly  similar  manner.  For  the  preparation  of 
alizarin  by  the  application  of  the  same  reaction,  see  p.  384. 

Reaction  LXXVI.  Addition  of  Hydroxyl  to  Ethylenic  Bonds.  (B.,  21, 
919  ;  A.,  268,  27.) — When  compounds  containing  ethylenic  linkages  are 
treated  with  mild  oxidising  agents,  e.g.,  bromine  and  caustic  potash, 
dilute  nitric  acid  and  especially  very  dilute  (2%)  potassium  permanganate 
solution,  addition  of  hydroxyl  at  the  double  bond  to  form  a  1  :  2-dihydroxy 
compound  occurs. 

02 

RjCH  :  CHR2  >  RiCH.CH.R^ 

"  H20     OH  OH 

If  stronger  oxidising  agents  be  thus  employed  the  carbon  chain  can  be 
broken  at  that  point. 

02 

RiCH.CH.R2->  RiCOOH  +  R2COOH. 
OH  OH 

This  reaction  is  used  to  determine  the  presence  and  position  of  double 
bonds  in  organic  compounds  ;  it  has  been  much  applied  to  the  elucidation 
of  the  structure  of  members  of  the  terpene  series. 

Preparation  140. — Phenyl-dihydroxy-propionic  Acid  (3-Phenyl-2  :  3- 
propan-diol  Acid). 

C6H5.CHOH.CHOH.COOH.       C9H10O4.  182. 

20  gms.  (1  mol.)  of  cinnamic  acid  (see  p.  107)  are  dissolved  in  3  litres 
of  5%  aqueous  caustic  soda  and  2  litres  (excess)  of  2%  aqueous  potassium 
permanganate  solution  are  added  with  good  cooling  and  mechanical 
stirring.  The  temperature  must  be  kept  at  —  5°  throughout.  The 
liquid  is  filtered,  nearly  neutralised  with  20%  hydrochloric  acid,  and  con- 
centrated until  the  dissolved  salts  begin  to  separate.  Neutralisation  is 
then  completed  with  cone,  hydrochloric  acid,  and  the  product  repeatedly 
extracted  with  large  quantities  of  ether  until  nothing  further  is  removed. 
Owing  to  the  solubility  of  phenyl-dihydroxy-propionic  acid  in  water 
this  will  necessitate  at  least  ten  extractions.  The  ethereal  solution  is 
evaporated,  and  the  residue  redissolved  in  ether,  the  solution  filtered, 
and  evaporated  to  low  bulk.    The  pure  acid  separates  on  cooling. 

02 

C6H5CH  :  CHCOOH  ->  C6H5CH(OH)CH(OH)COOH. 


206 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Yield. — 70%  theoretical  (17  gms.).  Colourless  needles  ;  soluble  in 
water  ;  somewhat  soluble  in  ether  ;  M.P.  141°.    (B.,  21,  919  ;  A.,  268,  27.) 

As  this  section  contains  the  most  important  methods  of  preparing 
alcohols,  methods  for  the  purification  of  commercial  methyl  and  ethyl 
alcohols  are  given  here. 

Purification  of  Methyl  Alcohol.  (Methanol). 

CH3OH.       CH40.  32. 

Methyl  alcohol  is  manufactured  by  the  dry  distillation  of  wood.  On 
this  account  the  commercial  article  is  usually  contaminated  with  acetone , 


Fig.  51. 


its  homologues  and  condensation  products,  and  also  with  acetaldehyde, 
methyl  acetate,  dimethyl  acetal,  etc.  It  is  purified  by  refluxing  with 
5%  of  solid  caustic  potash  on  a  water  bath  and  distilling.    It  is  then 


THE  LINKING  OF  OXYGEN  TO  CARBON 


207 


allowed  to  stand  for  24  hours  over  40%  of  freshly  burnt  quicklime,  and 
redistilled  from  a  water  bath,  the  distillate  being  collected  at  66° — 67°. 
This  removes  all  but  the  very  last  traces  of  water.  If  absolutely  pure 
methyl  alcohol  is  required  the  product  obtained  above  is  boiled  with  about 
1%  of  freshly  prepared  calcium  turnings  on  a  water  bath,  under  a  reflux 
condenser  (see  Fig.  51)  fitted  with  a  calcium  chloride  tube  until  the  solid 
deposit,  at  first  black,  becomes  almost  white.  It  is  then  distilled  into 
a  receiver  fitted  with  a  calcium  chloride  tube,  and  the  portion  passing 
over  at  a  constant  temperature  twice  redistilled  over  5%  of  calcium 
turnings,  using  a  column.  The  solid  formed  should  each  time  be  white, 
and  the  alcohol  should  all  distil  at  a  constant  temperature.  As  the 
anhydrous  alcohol  is  very  hygroscopic  it  must  not  be  exposed  to  air. 

Colourless  liquid  ;  spirituous  odour  ;  miscible  in  all  proportions  with 
water  ;  B.P.  66-5°  ;  D.  2,°  0-79133.    (B.,  41,  4322.) 

Purification  of  Ethyl  Alcohol.  (Ethanol). 

C2H5OH.       C2H60.  46. 

To  prepare  absolute  alcohol,  100  gms.  of  freshly  burnt  quicklime  in 
the  form  of  small  lumps  are  placed  in  a  500-c.c.  distilling  flask,  and  300  gms. 
of  rectified  spirits  added.  After  8  hours  the  alcohol  is  distilled  off  on  a 
water  bath  until  a  thermometer  in  the  neck  of  the  flask  indicates  80°. 
The  alcohol  so  obtained  still  contains  about  3%  of  water. 

For  absolutely  pure  alcohol  the  above  product  is  shaken  with  finely 
divided  silver  oxide.  This  oxidises  any  aldehyde  present  to  acetic  acid. 
Caustic  soda  is  added  to  bind  the  acid,  and  the  alcohol  distilled,  using  a 
good  column  (see  p.  21).  The  portion  passing  over  at  constant 
temperature  is  then  treated  with  calcium  turnings  in  the  same  way  as 
methyl  alcohol  (see  above).  The  anhydrous  alcohol  is  very  hygro- 
scopic, and  must  not  be  exposed  to  air. 

Colourless  liquid  ;  spirituous  odour  ;  miscible  with  water  in  all  propor- 
tions ;  binary  mixture  with  water  contains  75-57%  alcohol,  and  boils  at 
78-1°  at  760  nuns.  ;  B.P.  760  pure  alcohol,  78-3°  ;  B.P.21  13°  ;  D.  *  0-790. 
It  forms  a  ternary  mixture  with  benzene  and  water,  and  this  property 
can  be  utilised -to  obtain  absolute  alcohol.  (J.  C.  S.,  81,  707;  see 
Preparation  195 ;  B.,  38,  3612.) 


CHAPTER  XIV 


oxygen  to  carbon 
Oxide  Compounds 
Ethers 

This  section  deals  with  ethers  and  includes  all  the  more  usual  methods 
of  preparing  them  ;  they  are  for  the  most  part  chemically  inert  substances, 
and  are  not  of  very  great  importance  in  the  theory  of  organic  chemistry. 

Reaction  L  XXVII,  Action  of  Sulphuric  Acid  on  an  Alcohol  or  a  Mixture 
of  Alcohols.  (J.  Pharm.,  1,  97  ;  Phil.  Mag.  [3],  37,  350.)— This  is  the 
commercial  method  of  obtaining  the  most  important  of  the  ethers — di- 
ethyl ether — from  ethyl  alcohol.  The  reaction  occurs  in  two  stages,  the 
sulphuric  acid  acting  as  a  catalytic  rather  than  a  dehydrating  agent. 
In  the  first  stage  an  alkyl  hydrogen  sulphate  is  formed — this  yields  ether 
on  interaction  with  more  alcohol. 

C2H5OH  +  HoS04  =  C2H5.S04H  +  H20. 
C2H5.S04H  +  C2H5OH  =  C2H5.O.C2H5  +  H2S04. 

Thus,  in  theory,  a  limited  quantity  of  sulphuric  acid  can  convert  an 
unlimited  quantity  of  ethyl  alcohol  to  diethyl  ether,  but  in  practice, 
owing  to  side  reactions,  this  does  not  hold.  Sulphuric  acid  may  be 
replaced  by  phosphoric,  arsenic,  or  benzene-sulphonic  acids,  while  by 
using  a  mixture  of  alcohols  "  mixed  ethers  "  may  be  obtained  by  the  above 
reaction.  The  simple  ethers  are  formed  simultaneously,  however ;  so  for 
mixed  ethers  it  is  better  to  use  the  methods  given  on  pp.  209,  211, 
where  only  one  product  can  result.  As  a  catalyst  in  the  above  reaction, 
sand  or  aluminium  sulphate  may  be  employed.  The  method  is  applicable 
to  naphthols,  but  not  to  phenols. 

Peeparation  141.— Di-Ethyl  Ether  (Ethan-oxy-ethan). 

(C2H5)20.       C4H10O.  74. 

100  gms.  of  90%  alcohol  are  placed  in  a  ^-litre  distilling  flask,  and  under 
good  cooling,  180  gms.  (excess)  of  cone,  sulphuric  acid  are  slowly  added. 
The  flask,  fitted  with  a  thermometer  dipping  below  the  liquid,  and  a  tap- 
funnel  containing  alcohol,  is  attached  to  the  apparatus  for  the  distillation 
of  volatile  liquids  (see  Fig.  8),  and  is  heated  on  a  sand  bath  to  140° — 
145°,  and  the  temperature  kept  between  these  limits.  Alcohol  is  run  in 
from  the  tap-funnel  at  the  same  rate  as  the  liquid  distils  (two  drops  a 
second)  until  when  about  150  gms.  of  alcohol  have  been  added,  heating 
is  discontinued.  The  distillate  is  freed  from  sulphurous  acid  by  shaking 
twice  with  50  c.cs.  of  10%  caustic  soda  solution  and  from  alcohol  by 

208 


OXYGEN  TO  CARBON 


209 


shaking  twice  with  the  same  quantity  of  saturated  sodium  chloride 
solution.  The  residual  ether  is  dried  by  standing  8  hours  over 
anhydrous  calcium  chloride.  It  is  then  distilled  on  a  water  bath,  and 
collected  at  35°  C.  The  yield  is  improved  by  adding  10%  of  its  weight 
of  anhydrous  ferric  chloride,  aluminium  sulphate,  stannous  sulphate  or 
sand,  to  the  mixture  of  sulphuric  acid  and  alcohol,  the  added  substance 
acting  as  a  surface  catalyst.  The  ether  obtained  as  above  is  pure  enough 
for  ordinary  purposes  but,  when  absolutely  pure,  dry  ether  is  required  ; 
the  last  traces  of  alcohol  and  water  are  removed  by  allowing  the  ether  to 
stand  in  a  flask  over  a  mixture  of  2  parts  of  metallic  potassium  and 
1  part  of  metallic  sodium  in  the  form  of  thin  slices  or  wire.  The  flask  is 
fitted  with  a  calcium  chloride  tube  to  allow  hydrogen  to  escape  and 
prevent  the  ingress  of  moisture.  After  3  hours  the  ether  is  distilled  over 
fresh  metallic  sodium,  or  better,  phosphorus  pentoxide.  Owing  to  its 
volatility  and  inflammability  ether  should  always  be  distilled  from  a  water 
bath  in  the  apparatus  shown  for  the  distillation  of  volatile  liquids. 

C2H5OH  -f  H2S04  =  C2H5O.S02.OH  +  H20. 
C2H5OS02.OH  +  C2H5OH  =  (C2H5)2.0  +  H2SO,. 

Yield. — 80%  theoretical  (100  gms.).  Colourless  liquid  ;  characteristic 
odour  ;  miscible  with  alcohol  in  all  proportions  ;  slightly  soluble  in 
water  (1  in  10)  ;  B.P.76,)  3449°  ;  D.1/  0-720.  (J.  Pharm.,  1,  97  ;  Phil. 
Mag,  [3],  37,  350.) 

Purification  of  Commercial  Ether. 

The  chief  impurities  in  commercial  ether  are  alcohol  and  water.  It  con- 
tains traces  of  many,  however,  e.g.,  aldehyde,  methyl  alcohol,  due  to  the 
fact  that  it  is  made  from  methylated  spirit.  To  purify  it  for  special 
purposes — Grignard's  reaction,  etc. — it  is,  as  above,  allowed  to  stand  for 
8  hours  over  calcium  chloride,  treated  with  sodium,  or  a  mixture  of  sodium 
and  potassium,  and  then  distilled  over  sodium  or  phosphorus  pentoxide. 
The  presence  of  alcohol  in  ether  may  be  proved  by  shaking  the  latter 
with  a  spirit  soluble  dye,  e.g.,  aniline  violet.  If  alcohol  be  present  a 
blue  solution  is  obtained,  if  absent  none  of  the  dyestuff  passes  into  solution. 
Water  is  proved  to  be  present  by  the  cloud  which  is  formed  on  mixing 
wet  ether  with  carbon  disulphide. 

Reaction  L XXVIII.  Action  of  Alkyl  Halides  on  Alkali  Alcoholates  or 
Phenates.  (P.  K.  S,  7,  135  ;  J.  C.  S,  2,  198  ;  A,  78,  226,  152,  164  ;  B, 
12,  116.) — This  method  is  of  importance  as  indicating  the  structure  of 
ethers.  It  is  applicable  both  in  the  aromatic  and  aliphatic  series  ;  and 
can  be  used  to  obtain  the  ethers  corresponding  to  the  hypothetical  di- 
and  tri-hydric-alcohols,  in  which  more  than  one  hydroxyl  group  is  attached 
to  one  carbon. 

CH2C12  +  2C2H5ONa  =  CH2(OC2H5)2  +  2NaCl. 

Preparation  142. — Phenetole  (Ethoxy-benzene). 

C6H5.O.C2H5.       C8H10O.  122. 

A  500-c.c.  round  flask  containing  200  c.cs.  (excess)  of  absolute  ethyl 
s.o.c.  p 


210  SYSTEMATIC  ORGANIC  CHEMISTRY 


alcohol  is  attached  to  a  reflux  condenser,  and  8  gms.  (1  mol.)  of  sodium 
in  thin  slices  or  in  small  pieces  of  wire  are  added.  When  it  has  completely 
dissolved  31  gms.  (1  mol.)  of  phenol  and  75  gms.  (excess)  of  dry  ethyl 
iodide  are  added,  and  the  whole  refluxed  on  a  water  bath  until  the  solution 
is  no  longer  alkaline  (4  hours).  The  alcohol  and  excess  of  ethyl  iodide 
are  distilled  off  on  a  water  bath,  the  residue  treated  with  water  to 
dissolve  sodium  iodide,  and  extracted  with  ether.  After  drying  over 
calcium  chloride  the  ether  is  removed  on  a  water  bath  and  the  phenetole 
distilled  over  the  naked  flame,  the  distillate  being  collected  between 
168°— 173°. 

C6H5OH  +  C2H5ONa  =  C6H5ONa  +  C2H5OH. 
C6H5ONa  +  C2H5I  =  C6H5.O.C2H5  +  Nal. 

Yield. — Almost  theoretical  (40  gms.).  Colourless  liquid  ;  pungent 
smell ;  insoluble  in  water  ;  B.P.  172°  ;  D.!45  0«973.    (A.,  78,  226.) 

It  should  be  noted  that  owing  to  the  great  affinity  of  the  phenol  for 
sodium,  no  sodium  alcoholate  remains  to  react  with  the  ethyl  iodide. 
Diethyl  ether,  however,  may  be  prepared  in  a  similar  manner,  using  the 
same  quantities  of  sodium,  alcohol  and  ethyl  iodide  as  above.  The  ether 
and  excess  of  alcohol  are  distilled  off  and  the  ether  separated  from  the 
alcohol  by  the  addition  of  salt  solution.  Anisole  (phenylmethyl  ether 
B.P.  154°,  see  p.  211)  can  also  be  prepared  in  a  similar  way,  using  corre- 
sponding quantities  of  methyl  alcohol  and  methyl  iodide.  The  alkyl 
iodides  give  the  best  yields,  but  alkyl  chlorides  can  also  be  employed. 

Preparation  143. — Ethyl  Orthoformate  (Triethoxymethan). 

CH(OC2H5)3.       C7H1603.  148. 

58-5  gms.  (3  mols.)  of  metallic  sodium,  well  pressed  between  filter  paper, 
and  cut  into  thin  slices  or  pressed  into  wire  (see  p.  505)  are  placed  in  a 
dry  flask  of  about  1\  litres  capacity,  and  covered  with  a  layer  of  anhydrous 
ether  (see  p.  209).  The  flask  is  connected  to  a  condenser.  A  mixture 
of  117  gms.  (3  mols.)  of  absolute  alcohol  and  100  gms.  (1  mol.)  of  anhydrous 
chloroform  is  added  drop  by  drop  from  a  tap-funnel.  At  the  beginning 
the  reaction  is  violent,  and  the  flask  must  be  well  cooled  with  ice  ; 
sodium  chloride  separates  and  the  liquid  gradually  changes  to  a  brown 
colour.  To  complete  the  reaction  the  mass  is  warmed  on  a  water  bath 
until  all  the  sodium  present  is  converted  into  sodium  chloride.  The 
contents  of  the  flask  are  poured  into  water,  the  ethereal  solution  of  ethyl 
orthoformate  which  separates  is  removed,  washed  three  times  with  water, 
dehydrated  over  calcium  chloride,  the  ether  removed  on  a  water  bath,  and 
the  residue  distilled  over  a  bare  flame.  That  portion  of  the  distillate 
which  passes  over  above  100°  is  collected  separately  and  redistilled,  the 
fraction  143° — 150°  being  retained. 

CHC13  +  3C2H5ONa  =  CH(OC2H5)3  +  3NaCl. 

Yield. — 70%  theoretical  (85  gms.).    Colourless  liquid  ;   insoluble  in 
water  ;  soluble  in  ether  ;  B.P.  145°— 147°  ;  D.'  J  0-8964.    (P.  R.  S.,  7,  . 
135  ;  J.  C.  S:.  2.  198  ;  A.,  152,  164  ;  B.,  12,  116.) 


OXYGEN  TO  CARBON 


211 


Reaction  LXXIX.   Action  of  Dimethyl  Sulphate  on  Hydroxy  Compounds. 

(A.,  327,  114.) — This  is  the  most  important  method  of  preparing  methyl 
ethers — "  methylation  " — and  has  in  fact  almost  superseded  the  older 
method,  using  diazomethane.  The  substance  to  be  treated  is  dissolved 
or  suspended  in  cold  cone,  caustic  potash  solution  and  a  slight  excess  of 
dimethyl  sulphate  added.  Great  care  must  be  taken  in  working  with 
dimethyl  sulphate,  as  it  is  excessively  poisonous  (see  p.  64). 

RONa  +  (CH3)2S04  =  ROCH3  +  NaCH3S04. 

This  reagent  has  proved  especially  important  in  the  study  of  the 
constitution  of  the  sugars,  and  of  cellulose.  A  series  of  methyl-celluloses 
have  been  obtained,  and  by  the  study  of  their  hydrolysis,  or  decomposition 
in  a  vacuum,  some  light  has  been  thrown  on  the  structure  of  the  cellulose 
molecule  (J.  S.  C.  I.,  41,  362  E).  In  the  laboratory  dimethyl  sulphate 
is  much  employed  in  the  methylation  of  phenols  and  naphthols.  Diethyl 
sulphate  is  not  so  suitable  for  such  alkylations  as  its  lower  homologue. 

Prepakation  144. — Anisole  (Methoxybenzene). 

C6H5.O.CH3.       C7H80.  108. 

Caution  ! — Dimethyl  sulphate  is  very  poisonous  and  this  preparation 
must  be  carried  out  in  a  good  fume  cupboard. 

30gms.  (1  mol.)  of  phenol  dissolved  in  160  gms.  (excess)  of  10%  aqueous 
caustic  soda  solution  in  a  |-litre  round-bottomed  flask  are  carefully 
treated  with  50  c.cs.  of  commercial  dimethyl  sulphate,  and  the  whole 
continually  shaken.  The  flask  is  closed  by  a  cork  through  which  passes 
a  thermometer  and  a  glass  tube,  bent  in  a  spiral  to  prevent  liquid  spurting. 
The  beginning  of  the  reaction  is  shown  by  the  separation  of  an  upper 
layer  of  oil,  and  by  the  evolution  of  heat.  The  temperature  must  be  kept 
between  40° — 50°.  When  no  more  heat  is  evolved,  excess  of  dimethyl 
sulphate  is  destroyed  by  boiling  under  a  reflux  condenser  with  frequent 
shaking.  The  liquid  is  cooled  and  caustic  soda  added  until  an  alkaline 
reaction  is  obtained  ;  the  whole  is  extracted  with  ether  and  the  extract 
dried  by  shaking  with  anhydrous  potassium  carbonate  and  filtered. 
The  ether  is  removed  on  a  water  bath  and  the  residue  distilled,  the  fraction 
150°— 156°  being  retained. 

C6H5OH  +  NaOH  =  C6H5ONa  +  H20. 
C6H5ONa  +  (CH3)2S04  =  C6H5.O.CH3  +  Na.CH3.S04. 
(CH3)2S04  +  2NaOH  =  2CH3OH  +  Na2S04. 

Yield. — 90%  theoretical  (32  gms.).  Colourless  oil ;  pleasant  odour  ; 
insoluble  in  water  ;  soluble  in  ether ;  B.P.  154°  ;  D.1*  0-991.  (A.,  41,  71  ; 
48,  65  ;  78,  226  ;  327,  114.) 

Note. — The  vapour  of  dimethyl  sulphate  is  very  poisonous,  and  great 
care  should  be  taken  not  to  inhale  it.  It  should  only  be  used  in  a  fume 
cupboard  through  which  a  good  draught  is  passing.  It  must  never  be 
allowed  to  touch  the  skin,  and  gloves  and  an  overall  must  be  worn  when 
using  it.  These  should  be  removed  after  use.  Should  any  fall  on  the 
clothes  they  must  be  changed  immediately. 

p  2 


212  SYSTEMATIC  OKGANIC  CHEMISTRY 


The  next  preparation  illustrates  the  preparation  of  the  ethers  of  the 
polyhydric  phenols. 

Prepaeation  145.— Pyrogallol-Trimethyl-Ether  (1:2:  3-Trimethoxy- 
benzene). 

C6H3(OCH3)3[l  :  2  :  3].        C9H1203.  168. 

Caution  ! — Methyl  sulphate  is  very  poisonous.  (See  note  to  previous 
preparation.) 

20  gms.  (1  mol.)  of  pyrogallol  are  dissolved  in  30  gms.  (excess)  of  35% 
aqueous  caustic  soda  in  a  1 -litre  round-bottomed  flask  closed  with  a  cork, 
through  which  pass  a  thermometer  and  an  open  tube  bent  in  a  spiral 
to  prevent  spurting.  50  c.cs.  (excess)  of  commercial  dimethyl  sulphate 
are  gradually  added  with  continuous  shaking,  the  cork  being  momentarily 
removed.  The  temperature  is  not  allowed  to  rise  above  45°.  When 
heat  is  no  longer  evolved,  the  mixture  is  boiled  under  a  reflux  condenser, 
cooled,  made  alkaline  with  caustic  soda  if  necessary,  the  dark-coloured 
precipitate  filtered  at  the  pump,  and  well  washed  with  water.  It  is 
dissolved  in  ether,  filtered,  the  ether  removed  on  a  water  bath,  and  the 
residue  recrystallised  from  dilute  alcohol. 

(CH3)2SO, 

C6H3(ONa)3  [1:2:3]  >  C6H3(OCH3)3  [1:2.3]. 

Yield. — 70%  theoretical  (19  gms.).  Colourless  crystals  ;  insoluble  in 
water  ;  soluble  in  alcohol  and  ether  ;  M.P.  47°  ;  B.P.  235°.  (B.,  21,  607, 
2020  ;  R.,  126.) 

Peeparation  146. — /3-Naphthyl-Methyl  Ether  (2-Methoxy-naphthalene). 


-OCH3.       CnH10O.  158. 


(See  cautions  to  previous  two  preparations.) 

10  gms.  (1  mol.)  of  jS-naphthol  are  dissolved  in  40  gms.  (excess)  of  10% 
caustic  soda  solution,  and  the  cooled  liquid  mixed  with  8  c.cs.  of  commercial 
dimethyl  sulphate,  as  described  in  the  two  previous  preparations.  Gentle 
warming  may  be  needed  to  start  the  reaction.  The  required  ether  sepa- 
rates as  a  solid  which  is  filtered  off  after  boiling  and  making  alkaline  if 
necessary,  as  before.  The  precipitate  is  washed  with  water  and  recrystal- 
lised from  alcohol. 

(CH3)2S04 

C10H7OH[2]-  — t  C10H7.OCH3r2]. 

NaOH 

Yield. — Almost  theoretical  (11  gms.).  Lustrous  plates  ;  insoluble  in 
water  ;  soluble  in  ether  and  in  hot  alcohol ;  M.P.  71°.    (B.,  26,  2706.) 

The  following  preparations  show  the  way  in  which  cellulose, 
[C6H702(OH)3]rt,  can  be  methylated  to  give  compounds  having  the 
empirical  composition  : 

[C6H702(OH)2(OCH3)]it,  [C6H702(OH)(OCH3)2]ji  and  [C6H702(OCH3)3],, 

These  compounds  are  known  respectively  as  monomethyl  cellulose, 


OXYGEN  TO  CARBON 


213 


dimethyl  cellulose,  and  trimethyl  cellulose.    It  lias  not  yet  been  proved, 
however,  that  they  are  definite  chemical  substances. 
Preparation  147. — The  Methyl-celluloses. — (i.)  Monomethylcellulose. 

(CeH7Oa(OH)2(OCH8)  ),,       (C7H1205)f,  176,. 

50  gms.  (1  mol.)  of  well-picked  sliver  cotton  are  shaken  in  a  2 -litre 
flask,  closed,  as  described  in  Preparation  145,  with  180  c.cs.  (excess)  of 
23%  caustic  soda  ;  after  standing  for  1  hour  the  cotton  is  "  pounded  " 
in  a  glass  mortar.  It  is  returned  to  the  flask,  and  110  c.cs.  (excess)  of 
dimethyl  sulphate  gradually  added  (caution!  see  p.  64),  the  flask 
being  shaken  for  \  hour  between  each  addition.  When  no  further  evolu- 
tion of  heat  occurs,  the  flask  is  filled  with  water  and  the  contents  poured 
through  a  100-mesh  copper  gauze.  The  methyl  cotton  is  well  washed 
with  water  and  dried  in  an  air  oven. 

[C6H702(OH)3]u  ->  [C6H702(OH)2(OCH3)  ]n 

Yield. — Almost  theoretical  (53  gms.).  The  methyl  cotton  is  best 
characterised  by  its  methoxyi  content  (see  p.  476),  which  should  be 
close  to  17-65%  OCH3. 

(ii.)  Dimethylcellulose. 

[C6H702(OH)(OCH3)2],       (C8H1405),.  *  190,. 

50  gms.  (1  mol.)  of  monomethyl  cellulose,  prepared  as  above,  are  treated 
as  before  with  175  c.cs.  (excess)  of  20%  caustic  soda  solution  and  120  c.cs. 
of  dimethyl  sulphate  added.  The  subsequent  operations  are  as  above. 
The  dried  product  contains  about  28%  OCH3.  50  gms.  of  this  latter 
product  are  treated  with  400  gms.  of  water,  and  100  c.cs.  of  75%  caustic 
soda  solution  added  slowly  and  with  shaking.  100  c.cs.  of  dimethyl 
sulphate  are  added  under  cooling.  The  subsequent  operations  are  as 
in(i.) 

(C6H702(OH)2(OCH3)  )n  [C6H702(OH)(OCHs)a]B. 

Yield.— 90%  theoretical  (48  gms.). 

The  product  should  contain  close  to  32-63%  OCH3. 

(iii.)  Trimethylcellulose. 

[CeH702(OCH8)3],,       (09H1605V  204,, 

50  gms.  (1  mol.)  of  dimethyl  cellulose  are  treated  with  100  gms.  of  water, 
and  150  c.cs.  of  75%  aqueous  caustic  soda  solution  slowly  poured  in,  with 
good  shaking  and  cooling.  120  c.cs.  of  dimethyl  sulphate  are  added,  and 
the  whole  allowed  to  stand  overnight  and  filtered.  100  c.cs.  of  75% 
aqueous  caustic  soda  are  poured  in,  and  120  c.cs.  more  of  dimethyl  sulphate 
added,  as  before.    The  subsequent  operations  are  as  in  (ii.). 

[C6H702(OH)(OCH3)2](l  [C6H702(OCH3)3](, 

Yield. — 80%  theoretical  (45  gms.).  The  product  will  contain  about 
42-5%  methoxy  ;  the  theoretical  percentage  for  a  trimethyl  cellulose  is 


214  SYSTEMATIC  ORGANIC  CHEMISTRY 


45-6%,  but  it  is  impossible  to  methylate  cellulose  completely.  It  will 
be  noted  how  the  strength  of  the  caustic  soda  used  varies  with  the 
percentage  of  methoxyl  required  in  the  product. 

Reaction  LXXX.  Action  ol  very  Dilute  Methyl  Alcoholic  Hydrogen 
Chloride  on  the  Sugars.  (B.,  28,  1151.) — When  the  hexoses  are  heated  for 
a  long  time  at  100°  with  very  dilute  methyl  alcoholic  hydrogen  chloride, 
methyl  glucosides  are  produced.  This  synthesis  is  important,  as  it  indi- 
cates methods  for  the  synthesis  of  the  higher  sugars  (cane  sugar,  etc.). 
which  are  themselves  of  the  glucoside  type. 


CHOH 

CHOH 

CHOH 

CHOH 

CHO 
Glucose. 


CH.OH  +  HC1 


CH2OH 

I 

CHOH 

>  CHOH 

I 

CHOH 
CHOH 
CH(OCH3)2 


0. 


CHOH 

I 

CH 

CHOH 

.  CHOH 

^CHOCHa. 
Methyl-glucoside. 


Each  sugar  can  yield  two  glucosides  (a  and  /?)  since  the  carbon  to  which 
the  methoxy  group  becomes  attached  is  in  that  way  rendered  asymmetric. 
It  is  assumed  that  each  sugar  first  forms  a  dimethyl-acetal,  which  loses 
alcohol  to  yield  the  glucoside.  In  the  following  preparation  it  is  the 
a-glucose  which  preponderates  in  the  product. 

Preparation  148. — a-Methyl-Glucoside  (1-Methoxy-pentol-hexan). 

C6Hn05.OCH3.       C7H1406.  194. 

10  gms.  of  methyl  alcohol  dehydrated  and  purified,  as  described  on 
p.  206,  are  treated  with  dry  gaseous  hydrogen  chloride  until  a  little 
over  0-25  gm.  has  been  absorbed,  the  flask  being  cooled  in  ice  to  prevent 
loss  by  evaporation.  The  liquid  is  then  diluted  with  pure  anhydrous 
methyl  alcohol,  so  that  it  is  exactly  a  0-25%  solution  of  hydrogen  chloride 
in  the  alcohol.  25  gms.  (1  mol.)  of  finely  powdered  anhydrous  grape- 
sugar  are  then  added  to  100  gms.  (excess)  of  the  diluted  solution,  and  the 
liquid  refluxed  for  1  hour  until  the  sugar  has  all  dissolved.  The  liquid 
now  contains  an  intermediate  product,  thought  to  be  glucose-dimethyl- 
acetal ;  this  is  further  heated  in  a  sealed  tube  at  100°  for  60  hours,  and 
is  thus  converted  to  the  glucoside  (see  p.  38).  The  sealed  tube  used 
should  be  a  wide  one  and  should  be  placed  in  a  water  bath,  which  is  boiled 
behind  a  screen.  The  tube  is  then  opened  (see  p.  41),  and  the  solution 
evaporated  to  about  one-third  of  its  volume,  and  placed  in  a  freezing 
mixture.  After  standing  a  time,  or  sooner  if  "  inoculated  "  with  a  small 
crystal,  the  a-methyl-glucoside  separates  ;  it  is  filtered  off  after  12  hours. 
By  prolonged  heating  of  the  mother-liquor  to  100°  with  fresh  0-25% 
methyl-alcoholic  hydrogen  chloride  a  further  yield  of  glucoside  may  be 
prepared,    The  whole  product  is  recrystallised  from  ethyl  alcohol. 


OXYGEN  TO  CARBON 


215 


CH2OH 

CH3OH 

(CH0H)4  > 

!  HC1 
CHO 


Yield. — 40%  theoretical  (47  gms.).  Colourless  needles  ;  soluble  in  hot 
alcohol ;  M.P.  105°  ;  [a]D  +  157-6°.    (B.,  28,  1151  ;  34,  2899.) 

Reaction  LXXXI.  Action  of  Hydrogen  Chloride  on  a  Mixture  of  an 
Aldehyde  and  an  Alcohol.  (B.,  30,  3053  ;  31,  545.)— The  reaction  is  of 
the  same  type  as  the  preceding.  Under  the  influence  of  condensing  agents 
calcium  chloride,  hydrogen  chloride,  etc.,  aldehydes  combine  with  alcohols 
to  yield  the  ethers  of  the  hypothetical  dihydroxy  compounds  from  which 
the  aldehydes  are  derived.  Ketones  only  form  these  compounds  with 
difficulty. 

ECHO  +  RiCHjjOH  ~>  RCH(OCH2R1)2  +  H20. 
Preparation  149. — Di-Ethyl-Acetal  (1  :  1-Diethoxyethan). 

CH3CH  :  (OC2H5)2.       C6H1402.  118. 

15  gms.  of  anhydrous  calcium  chloride  and  a  few  drops  of  dilute  hydro- 
chloric acid  are  added  to  a  mixture  of  44  gms.  (1  mol.)  of  acetaldehyde 
and  100  gms.  (excess)  of  alcohol.  The  whole  is  allowed  to  stand  with 
occasional  shaking  for  1  hour,  when  the  lower  aqueous  layer  which  has 
separated  is  siphoned  off.  The  upper  layer  is  placed  over  15  gms.  more 
of  anhydrous  calcium  chloride,  and  after  standing  for  5  hours  with  constant 
shaking  the  separated  aqueous  layer  is  again  siphoned  off,  and  the  upper 
layer  added  to  a  third  15  gms.  of  calcium  chloride.  This  operation  is 
once  more  repeated  after  12  hours'  standing,  and  the  last  lot  allowed  to 
act  for  24  hours.  It  is  filtered  off  and  the  filtrate  fractionally  distilled. 
The  fraction  102°— 108°  is  collected  separately.  The  fraction  below  102° 
is  again  allowed  to  stand  over  calcium  chloride  for  24  hours,  and  again 
fractionated  as  before  ;  if  preferred  the  fractionation  may  be  performed 
under  reduced  pressure. 

CH3.CHO  +  2C2H5OH  =  CH3CH(OC2H5)2  +  H20. 

Yield. — 60%   theoretical   (70   gms.).    Colourless   liquid ;  aromatic 
odour  ;  soluble  in  18  volumes  of  water  at  25°  C.  ;  miscible  in  all  propor- 
1    tions  with  alcohol ;  B.P. 760  1  04°  ;  D.  24°  0-831.    (J.,  (1880),  694  ;  B.,  30, 
3053.) 

The  same  compound  may  be  obtained  by  dissolving  10  gms.  of  acetalde- 
hyde in  50  gms.  of  a  1%  absolute  alcoholic  solution  of  hydrogen  chloride, 
and  in  24  hours  extracting  the  solution  with  ether  after  neutralisation 
with  potassium  carbonate.  The  extract  is  dried  and  purified  by  distilla- 
tion as  before. 

Reaction  LXXXII.  Condensation  of  an  Aldehyde  with  itself  under  the 
Action  of  Mineral  Acids  or  of  Calcium  Chloride.    (A.,  27,  319  ;  162,  143  ; 


CH2OH 

CH2OH  CHOH 

I  I 
(CHOH)4   >  /CM 

I  /  I 

CH(OCH3)2  (CHOH)2 

\cHOCH3 


216  SYSTEMATIC  ORGANIC  CHEMISTEY 


203,  26,  43.) — If  acetaldehyde  be  treated  with,  calcium  chloride  or  mineral 
acids,  such  as  cone,  sulphuric  acid  or  gaseous  hydrogen  chloride, 
polymerisation  occurs  and  paraldehyde  is  formed.  A  certain  amount 
of  a  stereoisomer,  metaldehyde,  is  also  obtained ;  its  quantity  increases 
with  reduction  in  the  temperature  of  polymerisation. 


0  CH.CH3 

3CH3CHO  CH3CH^  yo 

0  CH.CH3 

Pkepakation  150. — Par-Aldehyde. 

/O.CHMe. 

'  CHMe<  >0.       C6H1203.  132. 

^O.CHMe/ 

132  gms.  (3  mols.)  of  freshly  distilled  absolute  acetaldehyde  are  placed 
in  a  flask  fitted  with  a  thermometer,  reflux  condenser,  and  gas  delivery 
tube,  and  the  whole  cooled  to  5°.  Dry  hydrogen  chloride  is  led  in  until 
an  absorption  of  6%  (8  gms.)  has  taken  place.  The  mixture  is  then 
allowed  to  stand  for  several  hours  at  room  temperature,  and  until  the 
temperature  has  risen  to  the  boiling  point  of  acetaldehyde,  21°,  when  it 
is  recooled  to  5°  and  allowed  to  stand  for  15  hours.  Some  metaldehyde 
has  by  then  separated,  and  is  filtered  off.  The  liquid  is  shaken  with  a 
saturated  solution  of  sodium  carbonate  to  remove  acid,  and  then  washed 
with  water.  It  is  dried  with  anhydrous  potassium  carbonate  and  frac- 
tionated, the  fraction  122° — 128°  being  retained.  The  distillation  can 
be  carried  out  under  reduced  pressure. 

3CH3.CHO  ->  CH3CH(OCH(CH3)  )20. 

Yield. — 70%  theoretical  (90  gms.).  Colourless  liquid ;  sparingly 
soluble  in  water  ;  M.P.  12-5°  ;  B.P.  184°  ;  metaldehyde  forms  bright 
feathery  crystals  which  readily  sublime.  (A.,  27,  319 ;  162,  143 ; 
203,  26,  43.) 

Reaction  LXXXIII.   Action  of  Caustic  Alkali  on  the  a,  ^-chlorhydrins. 

(A.  Spl.  (1861),  1,  221  ;  J.,  13,  456.)— When  the  chlorhydrins  which 
contain  chlorine  and  hydroxyl  attached  to  adjacent  carbons  are  heated 
with  caustic  alkali,  elimination  of  hydrochloric  acid  occurs  and  an  inner 
ether  or  oxide  is  obtained. 

E  R 

I  -I 
CHOH  CH 


CHC1 

I 


NaOH  =   |\n  +  NaCl  +  H20. 

\/° 
CH 

I 


These  oxides  are  unstable,  reacting  with  water  to  form  glycols,  with 
hydrochloric  acid  to  regenerate  the  chlorhydrin,  and  so  on.  The  simplest 
member  of  this  group,  ethylene  oxide,  is  especially  unstable,  it  behaves 


OXYGEN  TO  CARBON 


217 


almost  as  if  it  were  unsaturated  ;  it  will  even  absorb  hydrochloric  acid 
from  metallic  chlorides,  and  precipitate  the  base. 
Preparation  151. — Epichlorhydrin  (l-Chlor-2  :  3-mon-oxy-propan). 


CH2C1.CH  .  CH2.       C3H50C1.  92-5. 


100  gms.  (excess)  of  caustic  potash  are  dissolved  in  200  c.cs.  of  water,  and 
the  cooled  solution  poured  with  stirring  into  240  gms.  of  the  crude  dichlor- 
hydrin  obtained  in  Preparation  316  or  into  200  gms.  (1  mol.)  of  pure 
dichlorhydrin  ;  cooling  is  continued  throughout,  the  temperature  being 
kept  below  15°.  The  mixture  is  extracted  with  ether,  the  extract  washed 
with  a  little  water  dried  over  calcium  chloride,  the  ether  removed  on  a 
water  bath  and  the  residue  fractionated  using  a  column  (see  p.  21), 
the  fraction  114° — 120°  being  retained.  If  the  crude  dichlorhydrin  is  used, 
the  portion  boiling  above  this  temperature  is  mainly  aceto-dichlorhydrin, 
and  may  serve  for  the  further  preparation  of  epichlorhydrin  by  treat- 
ment with  potash.  If  a  pure  specimen  is  required,  it  may  be  purified  by 
distillation. 

CH2C1CH(0H).CH2C1  +  KOH  =  CH2.CH.CH2C1  +  KC1  +  H20. 

v 

O 

Yield. — 30%  theoretical  (45  gms.).  Colourless  mobile  liquid  ;  ethereal 
smell;  B.P.  117°  ;  D.  J  1-203.  (A.  Spl.,  (1861),  1,  221  ;  138,  297  ;  C. 
(1905),  [1],  12  ;  J.  13,  456.) 

Reaction  LXXXIV.  Addition  of  Phenols  to  Quinones.  (A.,  200,  251  ; 
215, 134  ;  B.,  24, 1341.) — Quinones  readily  react  with  1  mol.  of  ^>-di-hydric 
phenols  and  2  mols.  of  other  phenols  to  form  the  highly-coloured  ether 
compounds,  quinhydrones  and  |)henoquinones  respectively. 

O  OH  Q_ 


!! 

/\ 

+ 

OH 

y\ 

\/ 
II 

0 

OH 

0 

II 

/\ 

OH 

/\ 

\/ 

f  2 

II 

0 

OH  -O- 
Quinliydrone. 

OH 

X        O  / 


0 
OHX 


Phenoquinone. 

Quinhy  drone  can  also  be  prepared  from  quinone  or  quinol  by  half 
reduction  or  half  oxidation  respectively  (see  Preparation  152). 


218 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  152. — Quinhydrone. 
HO. 


C12H10O4.  218. 


HO 

Method  I. — 10  gms.  (1  mol.)  of  quinone  and  10  gms.  (1  mol.)  of  quinol 
are  separately  dissolved  in  the  minimum  quantity  of  water,  and  the 
solutions  mixed  and  warmed.  After  cooling,  the  precipitate  is  filtered 
off  and  washed  with  water. 

0  :  C6H4  :  0  +  C6H4(OH)2[l  :  4]  =  1  :  4(OH)2C6H4/   ^C6H4[1  :  4]. 

[4]  ° 

Yield. — Almost  theoretical  (20  gms.). 

Method  II. — 10  gms.  (2  mols.)  of  quinol  are  dissolved  in  water  and  heated 
with  an  aqueous  solution  of  14-5  gms.  (2  mols.)  of  ferric  chloride.  The 
quinhydrone  rapidly  separates.    It  is  filtered  off  and  washed  with  water. 

C6H4(0Ho)  +  2FeCl3  =  C6H402  +  2FeCL>  +  2HGL 
C6H402  +  C6H4(OH)2  =  (0H)2C6H4.02.C6H4. 

Yield, — Almost  theoretical  (10  gms.).  Lustrous  green  prisms  or 
leaflets  ;  quinone-like  odour  ;  soluble  in  warm  petroleum  ether  ;  in- 
soluble in  cold  water  ;  M.P.  171°.    (B.,  24,  1341  ;  28,  1615.) 

Preparation  153. — Phenoquinone. 

C6H5Ox  /OC6HB 

>C6H4<  C18H1604.  296. 

HO/  X0H. 

20  gms.  (1  mol.)  of  phenol  and  12  gms.  (1  mol.)  of  quinone  are  dissolved 
in  petroleum  ether  or  benzene  and  refluxed  for  10  minutes.  The  solution 
is  then  concentrated  on  a  water  bath  until  crystals  separate  on  cooling. 
They  are  filtered  off  and  washed  in  water. 

2C6H5OH  +  C6H40,  =  (C6H50)2(OH),C6H4. 

Yield. — Almost  theoretical  (32  gms.).  Red  acicular  crystals  ;  insoluble 
in  water  ;  somewhat  soluble  in  warm  petroleum  ether  ;  M.P.  71°  ;  sub- 
limes on  heating.    (A.,  204,  251  ;  215,  134.) 

The  above  preparation  can  also  be  performed  in  aqueous  solution. 

Resorcinol  quinone  and  pyrogallol  quinone  are  similarly  prepared  ;  they 
decompose  at  90°  and  above  120°  respectively. 


v 


CHAPTER  XV 


oxygen  to  carbon 
Oxy  Compounds 

Aldehydes,  Ketones,  and  Quinones. 

Aldehydes,  ketones  and  quinones  are  important ;  most  of  the  methods 
of  preparing  them  come  into  this  section.  The  reactions  on  which  those 
methods  are  based  are  chiefly  of  two  kinds — purely  oxidising  reactions, 
in  which  nascent  oxygen  directly  acts  {e.g.,  Preparation  439)  and 
hydrolytic  reactions,  in  which  the  oxygen  is  produced  by  the  decom- 
position of  a  molecule  of  water  (Preparation  154). 

Reaction  LXXXV.  Simultaneous  oxidation  and  Hydrolysis  o£  Mono- 
halogen  Compounds.  (A.,  22,  1  ;  143,  186.) — When  benzyl  chloride  or 
one  of  its  derivatives  is  heated  with  an  aqueous  solution  of  a  mild  oxidising 
agent,  such  as  copper  nitrate,  lead  nitrate,  etc.,  combined  hydrolysis  and 
oxidation  occurs,  and  benzaldehyde  or  one  of  its  derivatives  is  obtained. 

H20  0 
C6H5CH2C1   >  C6H5CH2OH  ->  C6H5CHO. 

Peeparation  154. — Benzaldehyde  (Phenyl-methanal). 

C6H5CHO.       C7H60.  106. 

50  gms.  (1  mol.)  of  benzylchloride  (see  p.  344),  50  gms.  (excess)  of 
copper  nitrate  and  300  c.cs.  of  water  are  refluxed  together  in  a  current  of 
carbon  dioxide  for  about  8  hours,  and  until  a  sample  of  the  oil  present 
contains  very  little  chlorine  (see  p.  502).  The  mixture  is  extracted 
with  ether,  the  ether  removed  on  a  water  bath,  and  the  residual  oil 
mechanically  shaken  for  1  hour  with  a  saturated  solution  of  sodium  bi- 
sulphite. After  standing  for  2  hours,  the  crystals  which  have  separated 
are  filtered  at  the  pump  and  washed  first  with  a  little  alcohol  and  then 
with  ether.  They  are  warmed  with  excess  of  10%  sulphuric  acid  ;  the 
aldehyde  which  separates  is  extracted  with  ether,  the  extract  dried  over 
anhydrous  sodium  sulphate,  the  ether  removed  on  a  water  bath  and  the 
residue  distilled  in  a  current  of  carbon  dioxide.  The  fraction  176° — 181° 
is  retained. 

2C6H5CH2C1  +  Cu(N03)2  =  2C6H5CHO  +  CuCl2  +  2HN02. 

Yield. — 40%  theoretical  (17  gms.).    Colourless  oil ;  characteristic 
odour  ;  M.P.  13-5°.    B.P.  179°  ;  D.  L|  1-0504.    (A.,  22,  1  ;  143,  186.) 
Reaction  LXXXVI.   Hydrolysis  of  certain  Di-halogen  Compounds. 

(A.  SpL,  2,  253  ;  A.,  139,  319  ;  D.R.P,  82927  ;  85493.)— When  di-halogen 

219 


220 


SYSTEMATIC  ORGANIC  CHEMISTRY 


compounds  containing  two  halogen  atoms  attached  to  the  one  carbon 
atom  are  boiled  with  water  in  presence  of  an  alkali  or  certain  metals, 
hydrolysis  occurs,  and  an  aldehyde  or  ketone  is  obtained. 

2H20 

E.CCl^!   >  E.C(OH)2E1  >  ECOKj. 

The  process  is  used  on  a  commercial  scale  to  prepare  benzaldehyde  by 
heating  benzal  chloride  with  an  aqueous  suspension  of  chalk  or  milk  of 
lime  under  pressure.  Water  is  sufficient  to  bring  about  hydrolysis,  the 
alkali  is  added  to  remove  the  hydrogen  chloride  formed,  and  so  prevent 
the  back  reaction  coming  into  play.  In  place  of  an  alkali,  a  trace  of 
iron  powder  can  be  used ;  the  reaction  here  takes  a  slightly  different 
course,  only  1  mol.  of  water  being  required  for  1  mol.  of  the  dichloride. 

Pkepaeation  155. — Benzaldehyde  (Phenyl-methanal). 

C6H5CHO.       C7H60.  106. 

Method  I. — 20  gms.  (1  mol.)  of  benzal  chloride  (see  p.  343)  are 
refluxed  for  4  hours  in  an  atmosphere  of  carbon  dioxide  with  200  c.cs.  of 
water  and  40  gms.  of  precipitated  chalk  in  a  round  flask  heated  on  an  oil 
bath  which  is  kept  at  130°.  The  whole  is  then  steam-distilled  in  an 
atmosphere  of  carbon  dioxide  (see  p.  23).  The  distillate  is  extracted 
with  ether,  the  ether  removed  on  a  water  bath  and  the  residual  benzalde- 
hyde purified  by  means  of  its  bisulphite  compound  as  described  in  Pre- 
paration 154. 

H20 

C6H5CHC12  >  C6H5CH(OH)2   >  C6H5CHO. 

Yield.— 70%  theoretical  (9  gms.).    (A.,  Spl.  2,  253  ;  139,  319.) 

Method  II. — 150  gms.  (1  mol.)  of  benzal  chloride  (see  p.  343)  are 
heated  in  a  round-bottomed  flask  to  30°  with  agitation ;  0-5  gms.  of  iron 
powder,  and  25  gms.  (excess)  of  water  are  then  added,  and  the  mixture 
cautiously  heated  until  hydrogen  chloride  is  evolved  (about  100°).  Heat- 
ing may  be  discontinued  until  the  action  subsides,  when  more  heat  is 
applied.  About  20  gms.  sodium  carbonate  are  added  to  give  an  alkaline 
reaction,  and  the  benzaldehyde  distilled  in  steam  in  an  atmosphere  of 
carbon  dioxide  and  purified  as  described  in  Preparation  154. 

C6H5CHC12  +  H20  ->  C6H5CHO  +  2HC1. 

Yield. — 80%  theoretical  (75  gms.).  Colourless  oil ;  characteristic 
odour  ;  insoluble  in  water  ;  soluble  in  ether  ;  M.P.  —  13-5°  ;  B.P.  179°  ; 
D.  J  1-0504.    (D.R.P.,  82927  ;  85493.) 

In  all  these  preparations  of  benzaldehyde  the  chief  loss  is  due  to  oxida- 
tion of  the  aldehyde  to  benzoic  acid.  The  acid  may  be  removed  from  the 
reaction  mixture  from  which  the  benzaldehyde  has  been  steam  distilled  by 
filtration  while  still  hot,  and  acidification  with  much  concentrated  hydro- 
chloric acid.    Benzoic  acid  separates  on  cooling. 

Reaction  LXXXVII.  Hydrolysis  of  certain  Anils.  (B.,  35,  1228; 
D.R.P.,  121745.) — When  derivatives  of  toluene  which  contain  negative 
groups  in  the  o-  and  ^-positions  are  treated  with  ^-nitroso-di-methyl- 


OXYGEN  TO  CARBON 


221 


aniline,  owing  to  the  activation  of  the  methyl  group  by  the  presence  of  the 
two  negative  groups,  condensation  to  an  anil  occurs. 

C6H3(N02)2(CH3)[2  :  4  :  1]  +  C6H4(NO).N(CH3)2)[l  :  4] 
=  C6H3(N02)2CH  :  N.C6H4N(CH3)2  +  H20. 

These  anils  are  readily  hydrolysed  by  acids  to  yield  derivatives  of 
benzaldehyde. 

H20 

C6H3(N02)2CH  :  N.C6H4N(CH3)2  > 

C6H3(N02)2CHO  +  H2N.C6H4N(CH3)2. 

Peeparation  156. — 2  :  4-Di-nitrobenzaldehyde  (2  :  4-Di-nitro-l-(oxy- 
methyl)-benzene). 

.      C6H3(N02)2(CHO)[2  :  4  :  1].        C7H405N2.  196. 

50  gms.  (1  mol.)  of  2  :  4-dinitrotoluene,  50  gms.  (excess)  of  £>-nitroso- 
dimethylaniline  and  90  gms.  of  crystallised  sodium  carbonate  are  refluxed 
on  a  water  bath  for  6  hours  with  300  c.cs.  of  alcohol.  The  anil  which 
separates  is  filtered  off,  washed  with  boiling  water,  and  recrystallised  from 
acetone.  The  whole  is  then  mechanically  shaken  for  4  hours  with  350  gms. 
(excess)  of  nitric  acid  (D.  1-17)  and  300  c.cs.  of  benzene,  filtered,  the  benzene 
layer  separated  and  the  solvent  removed  on  a  water  bath.  The  residue  is 
recrystallised  from  alcohol,  with  the  addition  of  animal  charcoal,  being 
precipitated  from  the  alcoholic  solution  by  dilution  with  water.  The 
crystals  which  separate  contain  1  mol.  of  alcohol  of  crystallisation ; 
this  they  lose  at  90°.  The  aqueous  layer  above  is  re-shaken  with  benzene 
and  nitric  acid,  and  worked  up  for  further  aldehyde  as  above. 

C6H3(N02)2(CH3)[2  :  4  :  1]  +  NOC6H4N(CH3)2[l  :  4J 

H20 

->  C6H3(N02)2CH  :  NC6H4N(CH3)2  > 

C6H3(N02)2CHO[2  :  4  :  1]  +  H2NC6H4N(CH3)2. 

Yield—  80%  theoretical  (42  gms.).  Yellowish  crystals  ;  insoluble  in 
water  ;  soluble  in  alcohol  and  benzene  ;  M.P.  72°  ;  B.P.  10  190°  ;  B.P. 
20  2  1  0°.    (B.,  35,  1228  ;  D.R.P.,  121745.) 

Reaction  LXXXVIII.  Action  of  Nitrous  Acid  on  the  Monoximes  of 
a-Di-ketones.  (A.,  274,  71.) — When  compounds  containing  the  group 
— CH2 — CO — •  are  treated  with  nitrous  acid  in  presence  of  sodium,  an  "  iso- 
nitroso  compound  "  identical  with  the  monoxime  of  the  corresponding 
a-di-ketone  is  obtained  (see  p.  105).  From  the  monoxime  by  the  further 
action  of  nitrous  acid  in  the  presence  of  glacial  acetic  acid,  the  di-ketone 
itself  is  formed. 

/CH2     HN09       /C:NOH   HNq2  /CO 

K<J  1  R<|   >  R<J 

\co  xco  \co. 

It  may  be  noted  that  aldehydes  and  ketones  are  usually  obtained  from 
the  corresponding  oximes,  phenyl-hydrazones,  semi-carbazones,  etc.,  by 
hydrolysis  with  dilute  mineral  acids. 


222 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  157. — Camphor-quinone  (1 :  3-Dioxyethylene-(l :  2  :  2- 
trimethyl)  -cyclo-pentan) . 

CH3 

CH2  C  CO 

!  i  i 

C(CH3)2  !         C10H14O2.  166. 

!              !  ! 
CH2  CH  CO. 

To  20  gms.  (1  mol.)  of  iso-nitroso-camphor  (see  p.  222)  dissolved  in 
35  c.cs.  of  glacial  acetic  acid,  9  gms.  (excess)  of  sodium  nitrite  in  20  c.cs.  of 
water  are  slowly  added  with  mechanical  stirring.  Initially  the  tempera- 
ture must  not  be  allowed  to  rise  above  20°,  but  when  the  evolution  of  gas 
ceases,  the  mixture  is  heated  until  no  more  gas  is  evolved.  When  cool, 
the  whole  is  poured  into  an  excess  of  cold  water,  and  the  precipitate 
filtered  off  at  the  pump,  well  washed  with  cold  water,  and  dried  on  a 
porous  plate.    It  is  then  sublimed  at  60°  (see  p.  28). 

/C :  NOH  .CO 
C8H14<  |  +  HN02  =  C8H14/  i     +  N20  +  H20. 

-co  V,o 

Yield. — 50%  theoretical  (9  gms.).  Yellow  needles  ;  sweetish  odour  ; 
insoluble  in  water  ;  sublimes  when  heated  ;  M.P.  198°.    (A.,  274,  71.) 

Reaction  LXXXIX.  Hydrolysis  of  Nitriles  to  Amides.  (B.,  18,  355.)— 
When  nitriles  are  heated  with  acids  or  alkalis  they  are  hydrolysed  to  the 
corresponding  acids  passing  intermediately  through  the  amides.  It  is 
possible  only  in  a  few  instances  (e.g.,  oxamide)  to  stop  the  hydrolysis  at 
this  intermediate  stage,  unless  alkaline  hydrogen  peroxide  be  employed, 
when  the  amide  is  obtained  almost  in  theoretical  yield.  Both  methods  of 
hydrolysis  are  illustrated  in  the  following  preparations. 

H20 

E.C  :  N   >  E.CO.NH2. 

Preparation  158. — Oxamide  (Di-amide  of  ethan-diacid). 

CONH2. 

C2H402N2.  88. 

CONH2. 

(To  be  carried  out  in  a  good  fume  cupboard.) 

25  gms.  (1  mol.)  of  crystallised  copper  sulphate  are  dissolved  in  75  c.cs. 
of  water  in  a  distilling  flask  heated  on  a  water  bath,  and  a  warm  solution 
of  13  gms.  (2  mols.)  of  98%  potassium  cyanide  in  25  c.cs.  of  water  is  added 
(caution  I  cyanogen  is  extremely  'poisonous).  The  evolved  cyanogen  is 
led  into  20  c.cs.  of  cold  cone,  hydrochloric  acid.  When  all  the  cyanide  has 
been  added,  the  second  equivalent  of  cyanogen  is  expelled  by  adding,  in 
the  same  way,  a  solution  of  16  gms.  (1  mol.)  of  ferric  chloride  in  20c.es.  of 
water.  Oxamide  now  separates  out,  provided  the  hydrochloric  acid  is 
kept  quite  cool.    It  is  washed  with  water. 

CN  CO.NH2. 
•     +  2H20  =  | 
CN  CO.NH2. 

Yield. — 50%  theoretical  (4-5  gms.).    White  crystalline  solid  ;  partly 


OXYGEN  TO  CARBON 


223 


sublimes  on  heating,  but  for  the  most  part  decomposes  ;  sparingly  soluble 
in  water  and  in  alcohols.    (B.,  18,  355.) 
Preparation  159. — Benzamide  (Amide  of  phenyl-methan  acid). 
C6H5.CO.NH2.       C7H7ON.  121. 

20  gms.  (1  mol.)  of  benzonitrile  are  added  to  300  c.cs.  (excess)  of  3%  (10 
volumes)  aqueous  hydrogen  peroxide  containing  5  c.cs.  of  2N  caustic  soda  . 
The  mixture  is  warmed  on  a  water  bath  to  40°,  and  then  shaken  in  an  un- 
corked bottle  until  the  oil  has  completely  disappeared.  The  precipitate 
which  forms  is  filtered  off  at  the  pump,  and  recrystallised  from  alcohol  or 
hot  water. 

2C6H5CN  +  2H202  =  2C6H5CO.NH2  +  02. 

Yield. — Theoretical  (21  gms.).    White  crystalline  powder  ;  soluble  in 
hot  water  ;  M.P.  128°.    (B.,  18,  355.) 
Reaction  XC.   Hydrolysis  of  the  Di-saccharoses.    (J.  pr.,  [2]  2,  1,  245  ; 

B.,  13,  1761  ;  28,  1429.) — When  the  di-saccharoses,  and  in  fact  all  the 
glucosides,  are  heated  with  mineral  acids,  they  are  hydrolysed  into  their 
component  monosaccharoses  or  into  their  component  monosaccharoses 
and  alcohols. 
In  this  way 

cane  sugar  yields  glucose  and  fructose, 

lactose  yields  glucose  and  galactose, 

maltose  yields  glucose, 

methyl  glucoside  yields  glucose  and  methyl  alcohol. 
These  hydrolyses  can  also  be  brought  about  by  means  of  various 
enzymes,  e.g.,  invertase  will  hydrolyse  cane  sugar,  maltase,  maltose,  and 
so  on. 

More  complicated  compounds  can  be  brought  within  the  scope  of  the 
reaction  ;  thus  starch  can  be  hydrolysed  to  glucose  in  this  way. 


CH9OH 


CH90H 


CHOH 


,CH 


CH 

/\ 
/  ' 
O  (CHOH), 


H90 


O 


(CHOH), 

V  ! 

XCH  


O 


CH2OH 


CHOH 

I 

CHOH 
CHOH 
CHOH 

CHO 

G-lucose. 


CHOH 

CHOH 

I 

CHOH 

i 

CO 

I 

CH2OH. 
Fructose. 


Cane-sugar. 

Preparation  160. — Glucose  (Pentolhexanal,  -\  h  +)• 

CHO 
H.COH 

HOC.H  C6H1206.  180. 

H.COH 
H.COH 
CH2OH. 

70  gms.  (excess)  of  fuming  hydrochloric  acid  (38%)  are  mixed  with 


224  SYSTEMATIC  ORGANIC  CHEMISTRY 


1,500  c.cs.  of  95%  alcohol,  and  the  whole  warmed  on  a  water  bath ;  500  gms. 
(1  mol.)  of  finely  powdered  cane  sugar  are  gradually  added  with  mechanical 
stirring,  the  temperature  being  kept  at  50°  throughout.  When  all  the 
sugar  has  dissolved,  the  liquid  is  filtered,  cooled,  seeded  with  0-5  gm.  of 
glucose  crystals,  and  allowed  to  stand  for  a  week  at  ordinary  temperatures. 
The  crystals  which  separate  are  filtered  off  at  the  pump,  washed  with 
absolute  alcohol,  and  recrystallised  by  dissolving  in  a  very  little  hot  water 
to  form  a  syrup,  and  adding  hot  methyl  or  ethyl  alcohol  until  the  solution 
becomes  turbid.  On  cooling,  the  sugar  which  separates  is  filtered  off  at 
the  pump,  and  washed  with  absolute  alcohol. 

C12H22O11  +  H20  =  C6H1206  +  C6H1206. 
Cane-sugar.         Glucose.  Fructose. 

Colourless  crystals  ;  verv  soluble  in  water  ;  insoluble  in  alcohol ;  M.P. 
146°.    (J.  pr.,  [2],  21,  245.) 

Reaction  XCI  (a).  Oxidation  oi  Aromatic  Hydrocarbons  to  Aldehydes 
by  the  action  of  Chromyl  Chloride  in  Carbon  Disulphide  Solution.  (Etard). 
(B.,  17, 1426  ;  21,  R.,  714.) — In  this  reaction  the  hydrocarbon  and  chromyl 
chloride  are  both  dissolved  in  carbon  disulphide,  and  the  solutions  care-  , 
fully  mixed.  An  explosive  intermediate  compound  is  precipitated,  and 
this  is  separated  and  decomposed  with  water  to  give  the  aldehyde.  The 
yields  are  very  good,  but  the  method  is  not  often  used  owing  to  the 
inconvenience  of  working  with  carbon  disulphide  and  the  dangerous 
nature  of  the  intermediate  compounds. 

RCHg  +  2Cr02Cl2  =  KCH.(OCr.Cl2OH)2. 
E.CH.(OCrCl2OH)2  +  3H20  =  ECHO  +  2CrO(OH)2  +  4HC1. 

Peepaeation  161. — Benzaldehyde  (Phenyl-methanal). 

C6H5.CHO.       C7H60.  106. 

(Great  caution  must  be  observed  in  performing  this  experiment.    No  light 
must  be  brought  near  the  apparatus.) 

10  gms.  (excess)  of  toluene  and  30  gms.  (2  mols.)  of  chromyl  chloride 
(see  p.  509)  are  each  dissolved  in  anhydrous  carbon  disulphide,  the  former 
in  50  gms.,  and  the  latter  in  120  gms.  ;  the  former  solution  is  placed  in  a 
litre  flask  fitted  with  a  thermometer  and  long  reflux  condenser,  and  the  T 
latter  is  added  in  10  c.cs.  quantities,  the  reaction  each  time  being  allowed 
to  moderate  before  further  addition.  Should  no  reaction  occur  on  the 
first  addition,  the  mixture  is  allowed  to  stand  for  15  minutes  before  further 
addition.  The  reaction  is  very  vigorous,  and  the  flask  must  be  cooled  by  ■ 
immersing  in  a  bath  of  ice- water,  so  that  the  temperature  of  the  mixture 
never  rises  above  45°.  When  addition  is  complete,  the  mixture  is  allowed 
to  stand  for  3  hours,  the  explosive  intermediate  compound  which  appears 
as  a  precipitate,  is  filtered  off  at  the  pump,  well  washed  with  anhydrous 
carbon  disulphide,  dried  by  blowing  air  through  it,  and  decomposed  by 
adding  in  small  quantities  to  1  litre  of  cold  water.  The  chromic  acid 
formed  is  reduced  with  gaseous  sulphur  dioxide,  and  the  liquid  steam- 
distilled  in  a  current  of  carbon  dioxide  to  remove  benzaldehyde,  which  is 


OXYGEN  TO  CARBON 


225 


extracted  from  the  distillate  with  ether.  The  extract  is  dried  over  calcium 
chloride,  the  ether  removed  on  a  water  bath,  and  the  residue  distilled  in  a 
current  of  carbon  dioxide,  the  fraction  177° — 182°  being  retained.  (For 
the  purification  of  the  aldehyde  by  means  of  its  bisulphite  compound,  see 
p.  219). 

Cr02Cl2  HoO 
C6H5CH3  •->C6H5CH(OCrCl2(OH)  )2  -  ->  C6H5.CHO. 

Yield. — Almost  theoretical  (116  gms.).  Colourless  oil ;  pleasant  odour  ; 
insoluble  in  water  ;  B.P.  179°  ;  D.A|  1-0504.    (B.,  17,  1426  ;  21  R.,  714.) 

Reaction  XCI.  (b)  Oxidation  of  Aromatic  Hydrocarbons  to  Aldehydes 
by  the  action  of  Chromic  Acid  in  Acetic  Anhydride  Solution.  (A.,  311, 
353  ;  D.R.P.,  121788.) — In  the  ordinary  way,  chromic  acid  oxidises  hydro- 
carbons to  aldehydes  and  then  to  acids.  But  if  acetic  anhydride  and  cone, 
sulphuric  acid  be  present,  the  di-acetyl  derivative  of  the  aldehyde  is  formed 
and  this  does  not  undergo  further  oxidation.  The  aldehyde  is  obtained 
from  the  di-ester  by  hydrolysis.  (Cf.  the  preparation  of  salicylaldehyde, 
P- 99.) 

02             (CH3CO)20  HC1 
RCH3  ->  ECHO  >  R.CH.(OCOCH3)2  >  R.CIIO. 

Preparation  162. — Zso-Phthalaldehyde. 

C6H4(CHO)2[l  :  3].       C8H602.  134. 

60  gms.  (excess)  of  chromic  acid  is  slowly  added,  with  good  agitation 
and  cooling  in  a  freezing  mixture,  to  15  gms.  (1  mol.)  of  m-xylene  mixed 
with  250  gms.  glacial  acetic  acid,  500  gms.  (excess)  acetic  anhydride,  and 
10  c.cs.  cone,  sulphuric  acid.  When  all  has  been  added,  the  mixture  is 
kept  at  0°  until  a  sample  gives  a  bulky  white  precipitate  when  shaken  with 
cold  water  till  the  anhydride  is  decomposed.,  It  is  then  poured  on  to 
powdered  ice  and  stirred,  until  the  oil  formed  solidifies.  The  ^so-phthal- 
aldehyde  tetracetate  is  filtered  off  and  recrystallised  from  methyl  alcohol 
(M.P.  101°).  The  crystallised  product  is  now  heated  under  a  reflux  for 
15  minutes  with  150  c.cs.  of  5%  hydrochloric  acid.  On  cooling,  the 
aldehyde  separates,  is  filtered  and  recrystallised  from  hot  water. 

C6H4(CH3)2  >  C6H4[CH(OCOCH3)2]2  >  C6H4(CHO)2. 

Yield. — -80%  theoretical  (15  gms.).  Colourless  needles  ;  soluble  in  hot 
water;  M.P.  89°.    (A.,  311,  353  ;  D.R.P.,  121788.) 

Reaction  XCI.  (c)  Oxidation  of  Aromatic  Hydrocarbons  to  Aldehydes 
by  the  action  of  Cerium  Dioxide  in  presence  of  Concentrated  Sulphuric  Acid. 

(D.R.P.,  158609.) — Cerium  dioxide  has  the  property  of  oxidising  aromatic 
hydrocarbons  to  aldehydes  and  no  further.  The  addition  of  a  reagent  to 
combine  with  the  aldehyde  group  as  formed  is  unnecessary. 

CeO, 

RCH3  >  R.CHO. 

Preparation  163. — Benzaldehyde  (Phenyl-methanal). 

C6H5CHO.       C7H60.  106. 

30  gms.  (1  mol.)  of  toluene  are  heated  to  60°  with  1,500  gms.  (excess)  of 
s.o.c.  Q 


226 


SYSTEMATIC  ORGANIC  CHEMISTRY 


sulphuric  acid  (D.  1-5)  in  a  2-litre  round-bottomed  flask  fitted  with  a 
reflux  condenser  and  mechanical  stirrer  (see  fig.  37).  250  gms.  (excess) 
of  cerium  dioxide  are  gradually  added,  and  the  temperature  allowed  to  * 
rise  to  90°.  When  no  more  dioxide  remains,  the  whole  is  steam-distilled 
until  no  more  benzaldehyde  passes  over.  Benzaldehyde  is  then  recovered 
from  the  distillate  as  in  Preparation  161. 

C6H5CH3  +  02  =  C6H5CHO  +  H20. 

Yield. — 70%  theoretical  (25  gms.).    Colourless  oil ;  pleasant  odour  ; 
insoluble  in  water  ;  B.P.  179°  ;  D.  ?  1-0504.    (D.R.P.,  158609.) 

Reaction  XCII.  Action  o£  Oxidising  Agents  on  Methylene  Groups  in 
Aromatic  Compounds.  (B,  6,  1347  ;  A.  Spl.  (1869),  7,  284  ;  A.,  279,  ' 
258.) — When  compounds  containing  methylene  groups  attached  to  two 
aromatic  residues  are  heated  with  oxidising  agents — chromic  acid  is  4 
usually  employed — the  two  hydrogens  of  each  methylene  group  are 
replaced  by  oxygen  to  yield  oxy-compounds,  which  have  some  or  all  of 
ihe  properties  of  ketones  and  of  quinones. 

C6H6CH2.CeH5  —■ ^  C6H5.CO.C6H5. 
C6H4<        >C6H4  — >  C6H4<  >C6H4. 

Preparation  164. — Anthraquinone  (s-di-phenylene-di-oxy-ethan). 

/co\  \m 

C6H4\        /C6H4,        C14H802.  208. 

A 

Anthracene  is  sublimed  with  superheated  steam  (see  p.  23)  at  200°.  y 
This  reduces  it  to  a  fine  state  of  division. 

100  gms.  (1  mol.)  of  moist  sublimed  anthracene  are  stirred  up  with 
2  litres  of  water  in  a  lead-lined  pot,  fitted  with  a  glass  agitator,  and  200 
gms.  (excess)  of  sodium  dichromate  are  dissolved  in  it  at  the  same  time., 
The  mixture  is  heated  to  80°,  and  600  gms.  (excess)  of  50%  sulphuric 
acid  are  added  from  a  dropping-funnel  during  10  hours.  The  presence  of 
chromic  acid  must  always  be  clearly  shown  (test  with  hydrogen  peroxide)?  ' 
The  mixture  is  then  boiled  for  2  hours,  evaporated  water  being  replaced 
at  intervals.  The  product  is  filtered  off,  thoroughly  washed  and 
dried.  It  is  heated  in  2 J  times  its  weight  of  cone,  sulphuric  acid  at  120° 
as  long  as  S02  is  evolved. 

After  3  hours  it  is  poured  into  3  times  its  weight  of  water,  and  the 
anthraquinone,  which  is  precipitated,  filtered  off  at  the  pump.    It  mayT.| 
be  further  purified  by  sublimation  at  250°. 

/CHv  02  /C0\ 

CfiH4<^       /C6H4  — >   C6H4^  \C6H4. 

Yield.-  90%  theoretical  (105  gms.).    Yellow  needles  ;   insoluble  irl? 
water ;   soluble  in  glacial  acetic  acid  ;   sublimes  on  heating  at  250° 


OXYGEN  TO  CARBON 


227 


M.P.  277°  ;  B.P.  382°  ;  is  an  important  intermediate  in  the  preparation 
of  vat  dyestuffs.    (B.,  6,  1347  ;  A.  SpL,  1869,  7,  284.) 

Anthraquinone  does  not  possess  the  properties  of  a  true  quinone. 

Reaction  XCIII.    Oxidation  of  Aromatic  Hydrocarbons  to  Quinones. 

(J.  C.  S.,  37,  634  ;  A.,  167,  139,  357.)— Although  benzene  does  not  react 
in  this  way  polynuclear  aromatic  hydrocarbons  can  be  oxidised  directly 
to  give  quinones  analogous  to  both  o-  and  j9-quinones.  The  oxidising 
agent  used  is  chromic  acid  in  glacial  acetic  acid.  The  amino  compounds, 
however,  give  better  yields  (see  Reaction  XCIV). 


0 

Preparation  165.— ct-Naphthaquinone  (s-Benz-benzoquinone). 

O 


C10H6O2.  158. 


10  gms.  (1  mol.)  of  naphthalene  dissolved  in  100  c.cs.  glacial  acetic  acid 
are  gradually  added  with  good  agitation  to  10  gms.  (excess)  of  chromic  acid 
dissolved  in  70  c.cs.  of  80%  acetic  acid,  the  whole  being  kept  at  0°.  After 
standing  for  4  days  at  the  ordinary  tern  perature  with  occasional  shaking, 
the  liquid  is  poured  into  a  litre  of  water.  Th  e  precipitated  naphthaquinone 
is  then  filtered,  washed  with  water  and  recrystallised  from  alcohol . 

C10H8  +  30  -»  C10H6O2  +  H20. 

Yield. — 40%  theoretical  (5  gms.)  (cf.  yield  in  Preparation  169).  Yellow 
plates  with  sharp  odour  ;  insoluble  in  water  ;  soluble  in  hot  alcohol ; 
volatile  in  steam  ;  M.P.  125°.    (J.  C.  S.,  37,  634  ;  A.,  167,  357.) 

(Cf.  ^9-benzoquinone,  p.  229.) 

Preparation  166.  —  Phenanthraquinone  (s-(Di-benz)-benz-or^o- 
quinone). 

O  0 

II  II 


CH.-O,.  208. 


30  gms.  (1  mol.)  of  phenanthrene  are  dissolved  in  150  gms.  of  warm 
glacial  acetic  acid,  80  gms.  (excess)  of  chromic  acid  dissolved  in 
about  250  gms.  of  glacial  acetic  acid  are  gradually  added.    This  latter 

Q  2 


228 


SYSTEMATIC  ORGANIC  CHEMISTRY 


solution  is  prepared  by  dissolving  the  chromic  acid  in  the  minimum 
quantity  of  water,  and  pouring  into  glacial  acetic  acid.  The  addition  is 
regulated  so  that  the  heat  of  reaction  keeps  the  mixture  just  on  the  boil 
throughout.  When  addition  is  complete  most  of  the  acetic  acid  is  dis- 
tilled off,  and  the  residue  treated  with  much  water.  The  precipitate  is 
filtered  at  the  pump,  washed  with  a  little  hot  water,  shaken  with  a  warm 
dilute  sodium  bisulphite  solution  and  filtered  ;  the  filtrate  is  warmed  on  a 
water  bath,  and  the  quinone  precipitated  by  addition  of  sulphuric  acid. 
This  precipitate  is  recrystallised  from  an  excess  of  boiling  alcohol. 

C14H10  +  30  =  C14H802  +  H20. 

Yield. — Almost  theoretical  (35  gms.).  Orange  needles  ;  odourless  ; 
not  volatile  in  steam  ;  insoluble  in  water  and  in  cold  alcohol ;  soluble  in 
glacial  acetic  acid  ;  M.P.  198°.    (A.,  167,  139.) 

(Cf.  o-benzoquinone,  p.  229.) 

Reaction  XCIV.  Oxidation  of  Primary  Aromatic  Amines  and  their  para- 
substituted  Derivatives  to  Quinones.  (A.,  27,  268;  194,  202;  211,  49; 
215,  125  ;  B.,  19,  1467  ;  20,  2283  ;  25,  982  ;  36,  4390.)— Many  primary 
aromatic  amines,  when  oxidised  with  chromic  acid,  readily  yield 
p-quinones,  aniline,  for  example,  giving  ^-benzoquinone. 


0 

NH2  || 


The  mechanism  of  this  reaction  is  not  simple,  but  is  probably  as 
follows  : — - 

C6H5NH2  ->  C6H5N  =  0  ->  C6H5NHOH 
Aniline.  Phenyl -am-        Phenyl  -hy- 

monium  oxide.  droxylamine. 

NH2.C6H4.OH  ->  0  :  C6H4  :  0. 
p-Aminophenol  Benzoquinone. 
(see  Prep.  137.) 

In  support  of  this  view  the  j>-amino  phenols  themselves  readily  yield  * 
quinones.  Also  most  ^-substituted  primary  amines,  e.g.,  ^-diamines, 
j9-alkylamines,  such  as  ^-toluidine,  sulphanilic  acid  and  its  derivatives,  1 
behave  similarly.  In  fact,  the  reaction  can  be  used  as  a  test  for 
^-substituted  primary  amines.  ^-Benzoquinone  is  usually  made  from 
aniline  ;  for  the  other  ^-quinones  the  j9-amino-phenols,  which  are  easily 
obtained  by  reduction  of  the  ^9-nitroso-phenols  and  of  azo  colours,  are 
employed.  These  reactions  also  apply,  but  not  so  widely,  in  the 
naphthalene  series. 


OXYGEN  TO  CARBON 


229 


Preparation  167.— p-Benzoquinone  (1 :  4-Di-oxy-2  :  5-hexadien). 

0 


CJLCL,  108. 


0 

To  50  gms.  (1  mol.)  of  aniline  dissolved  in  1,300  gms.  (excess)  of  25% 
sulphuric  acid  a  cold  20%  solution  of  50  gms.  of  sodium  dichromate  is 
slowly  added  in  3  hours,  with  good  cooling  and  mechanical  stirring.  The 
temperature  must  throughout  be  kept  below  4°.  When  all  the  dichromate 
has  been  dropped  in  the  whole  is  allowed  to  stand  for  24  hours,  and 
100  gms.  of  sodium  dichromate  added  in  the  same  manner  as  before. 
After  6  hours  the  liquid  is  extracted  6  times  with  its  own  volume  of 
ether,  the  latter  being  recovered  each  time  by  distillation  and  used  again. 
The  shaking  must  not  be  too  vigorous  as  the  mixture  tends  to  emulsify 
very  readily.  The  crude  product  from  the  ether  extraction  is  sublimed 
in  steam  (see  p.  23). 

If  sodium  dichromate  be  not  available  the  potassium  salt  may  be 
employed.  The  same  quantities  are  taken  as  with  the  sodium  salt,  but 
the  potassium  salt  is  added  in  the  form  of  powder,  and  not  in  aqueous 
solution. 

It  is  usual  to  treat  half  of  the  solution,  after  oxidation  is  complete,  with 
sulphur  dioxide  to  obtain  quinol  (see  p.  181).  As  quinone  is  more 
difficult  to  extract  with  ether  from  water  than  quinol,  the  whole  resulting 
solution  may  be  worked  up  for  quinol,  and  the  latter,  when  purified, 
oxidised  with  sodium  dichromate  solution  to  quinone. 

02 

C6H5NH2  >0:C6H4:  O, 

Yield. — 70%  theoretical  (40  gms.).  Yellow,  acicular  crystals ;  pene- 
trating odour  ;  slightly  soluble  in  water  ;  soluble  in  alcohol  and  ether  ; 
sublimes  on  heating ;  M.P.  116°.  (A.,  27,  268  ;  45,  354 ;  215,  125 ; 
B.,  19,  1467  ;  20,  2283.) 

In  an  exactly  similar  way  o-tolu-^>-quinone  (M.P.  67°)  may  be  prepared 
from  o-toluidine. 

The  next  preparation  illustrates  the  use  of  ^-diamines. 

Preparation  168.— Chloranil  (1 :  4-Di-oxy-2  :  3:5:  6-tetrachloro-2  :  5- 
cyclo-hexadien). 

0 

I! 

ci/\ci 

II 

0 

20  gms.  (1  mol.)  of  2  :  6-dichloro-4-nitraniHne  are  reduced  to  2:6. 


C602C14.  246. 


230  SYSTEMATIC  OKGANIC  CHEMISTRY 


dichloro-1  :  4-diaminobenzene  by  refluxing  with  800  c.cs.  (excess)  of  cone, 
hydrochloric  acid  and  30  gms.  (excess)  of  tin.  While  still  hot,  20  gms. 
(excess)  of  potassium  chlorate  are  gradually  added,  the  liquid  being 
maintained  at  the  boil  for  15  minutes  after  all  the  chlorate  has  been  added. 
The  liquid  is  diluted  with  much  water  and  filtered ;  the  precipitate  is  well 
washed  with  water,  dried,  and  recrystallised  from  boiling  toluene. 

02  +  ci2 

C6H2C12(NH2)2[2  :  6  :  1  :  4]  >  C6C1402. 

Yield. — 90%  theoretical  (22  gms.).  Yellow  leaflets  ;  characteristic 
odour  ;  insoluble  in  water  ;  sublimes  on  heating.    (B.,  36,  4390.) 

The  potassium  chlorate  here  both  oxidises  and  chlorinates.  If  chromic 
acid,  or  even  weaker  oxidising  agents,  be  employed  the  dichloro-quinone 
is  obtained.  The  oxidation  of  aminophenols  is  illustrated  in  the  follow- 
ing, in  which  nitrous  acid  serves  as  oxidising  agent. 

Preparation  169. — a-Naphthoquinone  (Benz-^-benzoquinone). 


158. 


II 

O 


To  20  gms.  (1  mol.)  of  finely  powdered  j9-amino  naphthol,  or  an  equiva- 
lent amount  of  one  of  its  salts  suspended  in  100  c.cs.  (excess)  of  hydro- 
chloric acid  (D.  1-05),  20  gms.  (excess)  of  sodium  nitrite  are  slowly  added. 
The  precipitate  formed  is  well  washed  with  water,  filtered,  and  dried  on  a 
porous  plate.  The  filtrate  is  extracted  with  ether,  the  extract  dried  over 
calcium  chloride,  filtered,  and  the  ether  removed  on  a  water  bath  at  60°. 
The  residue  and  the  dried  precipitate  are  recrystallised  from  petroleum 
ether. 

02 

C10H6(OH)(NH2)[1  :  4]  ->  C10H6O2[l  :  4]. 

Yield. — 80%  theoretical  (16  gms.).  Yellowish  plates  ;  characteristic 
odour  ;  soluble  in  hot  alcohol ;  volatile  in  steam ;  sublimes  at  100°  ; 
M.P.  125°.    (A.,  183,  242.) 

Preparation  170. — /^-Naphthoquinone  (Benz-o-benzoquinone). 


0 


158. 


50  gms.  (1  mol.)  of  finely  powdered  l-amino-2-naphthol  (see  p.  359) 
are  suspended  in  250  c.cs.  of  30%  sulphuric  acid,  and  30  gms.  (excess)  of 
10%  aqueous  potassium  or  sodium  dichromate  solution  slowly  added  with 


OXYGEN  TO  CARBON 


231 


mechanical  stirring,  the  temperature  being  maintained  at  0°.  The 
precipitate  is  filtered  off,  well  washed  with  water,  dried  on  a  porous  plate, 
and  recrystallised  from  petroleum  ether. 

C10H6(OH)(NH2)[1  :  2]  ->  C10H6O2[l  :  2]. 

Yield. — 75%  theoretical  (35  gms.).  Red  acicular  crystals  ;  odourless  ; 
non-volatile  in  steam  ;  M.P.  115°.  (A.,  189,  153  ;  194,  202  ;  211,  49  ; 
B.,  25,  982.) 

The  preparations  of  a-  and  ^-napthoquinone  should  be  compared  with 
those  of  phenanthraquinone,  and  the  corresponding  benzoquinones 
(see  p.  227). 


CHAPTER  XVI 


oxygen  to  carbon 
Hydroxy-Oxy  Compounds 
Acids. 

Various  hydrolytic  and  oxidation  reactions  give  rise  to  acids — the 
hydroxy-oxy  compounds  which  have  the  hydroxy  and  oxy  groups 
attached  to  the  one  carbon.  In  none  of  the  reactions  is  the  product  of 
necessity  a  hydroxy-oxy  compound  with  these  groups  attached  to 
different  carbons. 

Reaction  XCV.  Hydrolysis  of  Nitriles  (B.,  19,  1950 ;  20,  241,  592  ;  A,, 
258,  10.) — On  heating  with  aqueous  solutions  of  mineral  acids  or 
alkalis,  the  nitriles  are  converted  respectively  into  the  corresponding  acids 
or  into  the  alkali  salts  of  the  latter.  Aqueous  solutions  of  sodium  car- 
bonate can  also  be  employed  if  the  heating  be  performed  under  pressure. 
The  reaction  occurs  in  two  stages. 

H20  HOH 
EC  i  N  >  E.CO.  NH2  >  E.COOH. 

It  is  difficult  to  stop  the  hydrolysis  at  the  intermediate  amide  stage  (see 
p.  222). 

It  is  not  always  necessary  to  isolate  the  nitriles  on  their  formation  in 
order  to  hydrolyse  them  to  acids  (see  p.  153).  Still  without  isolation, 
the  acid  formed  can  be  simultaneously  esterified  by  using  for  hydrolysis 
aqueous  alcoholic  solutions  of  sulphuric  acid  (see  p.  249 ;  cf.  also 
p.  250). 

In  all  these  hydrolyses  water  is  always  the  hydrolysing  agent ;  the  acid 
or  alkali  acts  as  a  catalyst. 
Preparation  171. — Benzoic  Acid  (Phenyl-methan  acid.) 

C6H5.COOH.       C7H602.  122. 

20  gms.  (1  mol.)  of  phenyl  cyanide  (see  p.  149)  are  refluxed  with 
300  c.cs.  (excess)  of  25%  aqueous  caustic  potash  until  ammonia  ceases  to 
be  evolved.  The  solution  is  diluted  with  half  its  volume  of  water,  and 
cautiously  acidified  with  concentrated  hydrochloric  acid  under  good 
cooling.  The  precipitate  is  filtered  off  at  the  pump,  washed  with  cold 
water,  and  recrystallised  from  boiling  water. 

C6H5CN  +  KOH  +  H20  =  C6H5COOK  +  NH3. 

Yield. — 90%  theoretical  (21  gms.).    Colourless  needles  ;  soluble  in  hot 
water,  alcohol  and  ether  ;  volatile  in  steam  ;  sublimes  on  heating  ;  M.P.  i 
121°. 

232 


OXYGEN  TO  CARBON 


233 


Preparation  172.— ^J-Toluic  Acid  (l-Methyl-4-carboxyl-benzene). 

C6H4(CH3)(COOH)[I  :  4].       C8H802.  136. 

20  gms.  (1  mol.)  of  ^-tolu-nitrile  (see  p.  149)  are  refluxed  with  160  gms. 
(excess)  of  85%  sulphuric  acid,  until  crystals  appear  in  the  condenser  tube. 
The  well-cooled  mixture  is  diluted  with  two  volumes  of  water,  and  the 
precipitate  filtered  off  at  the  pump,  well  washed  with  cold  water,  and 
recrystallised  from  hot  water  or  dilute  aqueous  alcohol  with  the  addition 
of  a  little  animal  charcoal. 

H20 

C6H4(CH3)(CN)[1  :  4J  >  C6H4(CH3)(COOH)[l  :  4]. 

Yield. — 85%  theoretical  (14  gms.).    Colourless  crystals  ;  soluble  in  hot 
water  and  in  alcohol ;  M.P.  178°.    (A.,  258,  10.) 
Preparation  173. — Phenyl  Acetic  Acid  (Phenyl-ethan  acid). 

C6H5CH2COOH.       C8H802.  136. 

50  gms.  (1  mol.)  of  benzyl  cyanide  and  150  gms.  (excess)  of  80%  sul- 
phuric acid  are  placed  in  a  ^-litre  round-bottomed  flask  connected  by  a 
glass  tube  bent  twice  at  right  angles  with  a  second  ^-litre  round-bottomed 
flask  fitted  with  a  two-holed  cork.  The  end  of  the  tube  is  flush  with  the 
cork  in  one  hole.  Through  the  second  hole  passes  a  vertical  glass  tube, 
50  cms.  long,  dipping  just  below  the  surface  of  250  c.cs.  of  water  in  the  flask. 
In  the  middle  of  this  tube  a  large  bulb  is  blown.  The  whole  apparatus  is 
fitted  up  in  a  fume  cupboard.  The  mixture  is  gently  heated  by  a  naked 
flame,  until  small  bubbles  are  seen  to  rise  from  the  surface  of  the  lower 
layer  of  acid.  In  a  few  minutes  a  vigorous  reaction  begins,  the  liquid  in 
the  flask  boils,  and  a  small  quantity  of  benzyl  cyanide  distils  over  into  the 
second  flask,  some  of  the  water  in  which  is  forced  up  into  the  bulb.  When 
the  reaction  is  over,  the  flask  is  again  heated  for  3  minutes  and  allowed  to 
cool,  its  contents  solidifying  in  so  doing.  The  solid  residue  is  washed  with 
cold  water,  dissolved  in  hot  water,  the  solution  neutralised  with  sodium 
carbonate,  filtered  hot,  the  nitrate  acidified  with  dilute  sulphuric  acid,  and 
allowed  to  stand.  The  crystals  which  separate  are  filtered  off,  washed 
with  cold  water,  and  recrystallised  from  hot  water. 

2C6H5CH2.CN  +  4H20  +  H2S04  =  2C6H5CH2COOH  +  (NH4)2S04. 

Yield. — 80%  theoretical  (46  gms.).    Colourless  thin  laminated  crystals  ; 
soluble  in  hot  water  ;   M.P.  76-5  ;   B.P.  262°  ;   K  =  0-0056.    (B.,  19, 
,  1950  ;  20,  592.) 

Preparation  174. — a-Naphthoic  Acid  (l-Carboxyl-naphthalene)o 

COOH 


C13LH802.  172. 


r     15  gms.  (1  mol.)  of  a-naphthonitrile,  10  gms.  (excess)  of  caustic  soda, 
and  75  c.cs.  of  95%  alcohol  are  heated  in  a  sealed  tube  (see  p.  38) 


234  SYSTEMATIC  OKGANIC  CHEMISTRY 


at  170°  for  5  hours.  On  opening,  the  contents  of  the  tube  are  diluted 
with  5  volumes  of  water,  and  carefully  acidified  with  cone,  hydrochloric 
acid.  The  precipitate  is  filtered  at  the  pump,  washed  with  water,  and 
recrystallised  from  alcohol. 

C10H7CN  +  NaOH  +  H20  =  C10H7COONa  +  NH3. 

Yield. — 90%  theoretical  (15  gms.).  Colourless  crystals  ;  insoluble  in 
water  ;  soluble  in  alcohol ;  M.P.  160°.    (B.,  20,  241.) 

Reaction  XCVI.  Hydrolysis  of  Esters  to  Acids.  (A.,  186,  161 ;  204,  127 ; 
215,  26.)— When  esters  are  heated  with  water,  hydrolysis  occurs,  but  does 
not  go  to  completion,  the  reaction  being  reversible. 

K.CO.ORi  +  H20  ^  ECOOH  +  HOR^ 

If,  however,  aqueous  or  alcoholic  caustic  alkali  be  used,  by  combining 
with  the  acid  as  formed,  it  shifts  the  equilibrium  point  of  the  reaction,  and 
almost  complete  hydrolysis  occurs.  This  reaction  could  also  have  been 
dealt  with  under  Chapter  XIII,  since  alcohols  are  simultaneously  formed  ; 
however,  the  hydrolysis  is  more  usually  undertaken  to  obtain  the  acid. 
Other  special  cases  of  hydrolysis  have  been  dealt  with  elsewhere  (see 
Reaction  LVIL).  The  general  method  of  procedure  will  be  clear  from 
the  following. 

Pkepaeation  175. — Acetic  Acid  (Ethan-acid). 

CH3.COOH.       C2H402.  60. 

20  gms.  (1  mol.)  of  ethyl  acetate  (see  p.  249)  are  refluxed  with  80  gms. 
(excess)  of  25%  aqueous  caustic  potash  for  1  hour,  until  the  layer  of 
ester  has  disappeared,  and  the  mixture  no  longer  smells  of  it.  The  whole 
is  then  distilled  to  100°  ;  ethyl  alcohol  can  be  separated  from  the  distillate 
by  addition  of  anhydrous  potassium  carbonate.  The  residue  in  the  flask 
is  neutralised  with  dilute  sulphuric  acid  and  evaporated  to  dryness  on  a 
water  bath.  The  solid  residue  is  powdered  and  redistilled  with  50  gms. 
of  cone,  sulphuric  acid  to  130°,  and  the  distillate  fractionated  between 
115°  and  120°. 

CH3COOC2H5  +  KOH  =  CH3COOK  +  C2H5OH. 
2CH3COOK  +  H2S04  =  2CH3COOH  +  K2S04. 

Yield. — 90%  theoretical  (12  gms.).  Colourless  liquid  or  crystals  ; 
characteristic  odour;  miscible  with  water;  M.P.  16-7°;  B.P.  119°; 
D.  *  1-055.    (Phil.  Trans,,  156,  37  ;  BL,  33,  350.) 

Pkepaeation  176. — Ethyl-malonic  Acid  (Ethyl-propan  diacid). 

C2H5.CH(COOH)2.       C5H804.  132. 

20  gms.  (1  mol.)  of  di-ethyl-malonate  (see  p.  251)  are  gradually  added 
to  50  gms.  (excess)  of  50%  aqueous  caustic  potash  in  a  flask  fitted  with  a 
reflux  condenser,  and  cooled  in  water.  The  mixture  so  obtained  is  heated 
on  a  water  bath  with  shaking  until,  after  a  vigorous  reaction,  complete 
liquefaction  has  occurred  (1  hour).  The  liquid  is  cooled,  diluted  with  an 
equal  volume  of  water,  acidified  with  cone,  hydrochloric  acid,  and  extracted 
with  ether.    The  extract  is  dried  over  anhydrous  sodium  sulphate, 


OXYGEN  TO  CARBON 


235 


filtered,  the  ether  removed  on  a  water  bath,  and  the  residue  recrystallised 
from  benzene. 

The  ethyl-malonic  acid  can  also  be  worked  up  by  precipitating  its  cal- 
cium salt  from  the  neutralised  solution  by  addition  of  a  concentrated 
solution  of  calcium  chloride,  and  treating  the  solid  salt  with  cone,  hydro- 
chloric acid,  extracting  the  liberated  acid  with  ether,  and  proceeding  as 
above. 

C2H5CH(COOC2H5)2  +  2KOH  =  C2H5CH(COOK)2  +  2C2H5OH. 

Yield. — 85%  theoretical  (12  gms.).  Colourless  prisms  ;  soluble  in 
water,  alcohol  and  ether  ;  M.P.  112°.    (A.,  204,  134.) 

Like  all  the  malonic  acids,  this  acid  loses  carbon  dioxide  on  heating, 
yielding  butyric  acid,  B.P.  163°.  The  reaction  is  carried  out  by  heating 
10  gms.  of  the  acid  in  a  reflux  apparatus  to  180°  until  carbon  dioxide  is 
no  longer  evolved  (J  hour).  The  residue  is  fractionated  for  butyric  acid 
between  160°  and  165°. 

Pkepakation  177. — Benzylmalonic  Acid  (Benzyl-propan  diacid). 

C6H5.CH2.CH(COOH)2.       C10H10O4.  194. 

30  gms.  (1  mol.)  of  benzylmalonic  ester  (cf.  p.  136)  are  vigorously 
shaken  in  a  250-c.c.  round-bottomed  flask  with  35  gms.  (excess)  of  33% 
aqueous  caustic  potash,  the  mixture  warmed  until  solution  occurs,  and 
then  heated  for  1  hour  on  a  water  bath,  no  condenser  being  used.  Oily 
by-products  are  extracted  with  ether,  the  liquid  is  made  faintly  acid  with 
dilute  hydrochloric  acid,  and  the  benzylmalonic  acid  liberated  is  extracted 
with  ether,  several  treatments  being  necessary.  The  extract  is  dried  over 
anhydrous  sodium  sulphate  and  filtered,  the  ether  removed  on  a  water 
bath,  and  the  residue  recrystallised  from  benzene. 

C6H5CH2CH(COOC2H5)2  +  2KOH  =  C6H5CH2CH(COOK)2  +  2C2H5OH. 

Yield. — 85%  theoretical  (20  gms.).  Colourless  crystals  ;  insoluble  in 
water  ;  M.P.  117°  (Coir.).    (A.,  204,  174.) 

This  acid  on  heating  to  180°  loses  carbon  dioxide  and  yields  hydro- 
cinnamic  acid  (M.P.  47°)  in  almost  theoretical  yield. 

The  following  hydrolysis  is  important  in  the  synthesis  of  collidine  (see 
p.  404). 

Preparation  178.- — Potassium  Collidine  Dicarboxylate  (Di-potassium- 
2:4:  6-trimethyl-pyridine-3  :  5-dicarboxylate). 

C.CH3 

KO.OCc/^Sc-CO.OK. 

I  C14H904NK2.  285. 


N 


10  gms.  (1  mol.)  of  diethyl-collidine  dicarboxylate  are  refluxed  on  a 
water  bath  for  4  hours  with  about  10  times  the  volume  (excess)  of 
alcoholic  potash  (2-5  N  approx.).  The  alcoholic  solution  is  decanted 
from  the  separated  potassium  salt,  a  further  yield  of  which  is  obtained  by 


236 


SYSTEMATIC  ORGANIC  CHEMISTRY 


adding  ether  to  the  alcoholic  solution.  The  total  product  is  washed  with 
alcohol  then  with  ether  and  dried. 

C5N(CH3)3(COOC2H5)2  -  2KOH  =  C5N(CH3)3(COOK)2  -  2C2H5OH. 

Yield. — Almost  theoretical  (11  gms.).  White  crystalline  mass  ;  in- 
soluble in  ether.    (A..  215.  26.) 

Reaction  XCVII.  Hydrolysis  of  Amides,  Acyl  Chlorides,  and  Acid 
Anhydrides.  (A..  1883  73  :  B..  26.  R..  773  :  2S.  R..  917.  32.  1118.) — All 
these  compounds  on  hydrolysis  yield  acids.  The  anhydrides  are  hydro- 
lysed  by  treatment  with  water  or  dilute  alkali,  the  acid  chlorides,  are 
usually  very  rapidly  hydrolysed  by  water,  but  in  the  aromatic  series  10% 
caustic  alkali  is  sometimes  necessary.  The  amides  are  boiled  with  caustic 
alkali  solution  (10° 0),  or  with  cone,  hydrochloric  or  sulphuric  acid.  They 
are.  especially  the  substituted  aromatic  amides,  very  resistant  to  the 
•Action  of  acids,  so  that  the  former  method  is  the  better.  Another  method 
is  to  dissolve  the  amide  in  cone,  sulphuric  acid,  and  add  sodium  nitrite 
in  the  cold,  afterwards  gently  warming.  Sometimes  dilute  sulphuric 
acid  and  addition  of  the  nitrite  in  the  warm  gives  better  results. 

e6H5COXH2  -f  O  :  NOH  =  C6H5COOH  +  N2  -  H20. 

Preparation  179. — Citraconic  Acid  ((7^-3-carboxyl-2-buten  acid). 

CH3 

C.COOH        C5H604.  130. 

II 

CH.COOH. 

3-2  gms.  (1  mol.)  of  water  are  added  to  20  gms.  (1  mol.)  of  citraconic 
anhydride,  and  the  mixture  well  stirred.  The  whole  solidifies,  on  standing, 
to  a  mass  of  crystals  which  are  dried  on  a  porous  plate. 

CH3  CH3 

ceo  ceo. oh 

;         +  H20 

CH.CO  CH. CO. OH. 

Yield. — Theoretical  (23  gms.).  Colourless  crystals  :  soluble  in  ether 
and  chloroform :  very  soluble  in  water :  M.P.  85° :  K  =  0-310. 
(A.,  188.  73.) 

Reaction  XCVIII.  Simultaneous  Oxidation  and  Hydrolysis  of  Benzyl 
and  Benzal  Chlorides  and  their  Derivatives.  (BL.  7.  100  ;  B..  10.  1275). — 
If  benzyl  or  benzal  chlorides,  or  their  derivatives,  be  rerluxed  with  an 
aqueous  solution  containing  sodium  carbonate  and  potassium  perman- 
ganate,, simultaneous  hydrolysis  and  oxidation  occurs,  and  benzoic  acid 
or  one  of  its  derivatives  is  produced. 

NaoCo,  02 

CflH5.CH,.Cl    C6H5CH,OH  — ■>  C6H5COOH. 

Na2C03  o„ 

C6H5.CH.C12  ►  C6H5.CHO  V  C6H5COOH. 


OXYGEN  TO  CARBON 


237 


Preparation  180. — Benzoic  Acid  (Phenyl-methari  acid). 

C6H5COOH.       C7H602.  122. 

To  a  mixture  of  10  gms.  (6  mols.)  of  benzyl  chloride,  8  gms.  (excess)  of 
anhydrous  sodium  carbonate,  and  150  c.cs.  of  water  boiling  under  a  reflux 
condenser,  17  gms.  (8  mols.)  of  potassium  permanganate  in  250  c.cs.  of 
water  are  added  gradually,  and  the  boiling  continued  until  the  colour  of 
the  permanganate  has  been  discharged.  Sulphur  dioxide  is  then  bubbled 
through  the  warm  liquid  until  the  precipitated  manganese  dioxide  has 
completely  dissolved.  On  cooling,  benzoic  acid  separates  ;  it  is  filtered 
at  the  pump,  washed  with  a  little  cold  water,  and  recrystallised  from  hot 
water. 

6C6H5CH2C1  +  3Na2C03  +  3H20  =  6C6H5CH2OH  +  6NaCl  +  3C02. 
6C6H5CH2OH  +  8KMn04  =  6C6H5COOK  +  8Mn02  +  2KOH  +  8H20. 

Yield. — Theoretical  (9  gms.).  Colourless  needles ;  soluble  in  hot 
water,  alcohol  and  ether  ;  volatile  in  steam  ;  on  heating  melts  and 
sublimes  ;  M.P.  121°.    (Bl.,  7,  100  ;  B.,  10,  1275.) 

Reaction  XCIX.  Oxidation  of  certain  Carbon  Compounds  to  less  com- 
plex Compounds.  (J.  pr.,  75,  146.) — Complex  carbon  compounds  under 
vigorous  oxidisation  break  up  yielding  simpler  compounds  usually  highly 
oxygenated.  These  reactions  are  difficult  to  represent  by  means  of 
equations,  though  a  study  of  the  structure  of  the  original  compound  will 
indicate  how  the  products  come  to  be  formed.  The  structure  of  a  com- 
pound can  often  be  deduced  from  its  oxidation  products. 

Oxalic  acid  is  a  frequent  product  of  vigorous  oxidation,  especially  of 
members  of  the  sugar  group.  Its  formation  can  be  promoted  by  the  use 
of  catalysts. 

Preparation  181. — Oxalic  Acid  (Ethan  diacid). 

COOH 

(  +  2H20).       C2H204(  +  H402).       90(  +  36). 

COGH 

140  c.cs.  (excess)  of  cone,  nitric  acid  and  0-1  gm.  of  vanadium  pent- 
oxide  are  gently  warmed  in  a  1 -litre  round-bottomed  flask  on  a  water 
bath.  The  flask  is  then  removed  to  a  fume  cupboard,  and  20  gms.  (1  mol.) 
of  cane  sugar  are  added  all  at  once.  As  soon  as  brown  fumes  are  evolved 
in  large  quantities,  the  flask  is  placed  in  cold  water,  and  allowed  to  stand 
24  hours,  when  the  crystals  which  have  separated  are  filtered  off.  A 
further  small  quantity  may  be  obtained  by  allowing  the  mother  liquors 
to  stand.  The  crystals  are  drained  on  a  small  porcelain  funnel  without 
filter  paper,  and  recrystallised  from  a  very  small  quantity  of  water. 

C12H22On  +  902  =  6(COOH)2  +  5H20. 

Yield. — 25%  theoretical  (20  gms.).  Colourless  needles  ;  soluble  in 
water  and  alcohol ;  sparingly  soluble  in  ether  ;  water  of  crystallisation 
given  off  at  100°— 105°  ;  M.P.  101-5°  ;  K  =  10.    (J.  pr.,  75,  146.) 

Reaction  C.  Oxidation  of  the  Side  chain  in  Aromatic  Compounds.  (A., 
122,  184  ;  133,  41  ;  137,  308  ;  141,  144  ;  147,  292  ;  B.,  7,  1057  ;  19,  705  ; 


238 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Z.  Ch.,  4,  119)  (Fittig). — When  aromatic  compounds  containing  aliphatic 
side  chains  attached  to  the  nucleus  are  treated  with  certain  oxidising 
agents  (potassium  permanganate,  dilute  nitric  acid,  and  chromic  acid), 
the  side  chain  is  oxidised  until  only  a  carboxylic  group  attached  to  the 
nucleus  remains  ;  the  end  methyl  group,  if  there  be  several  carbon  atoms 
present,  being  first  oxidised  to  carboxyl  and  split  off,  and  so  on  down  to 
the  first.  If  several  side  chains  be  present  the  results  vary  with  the 
reagent  and  the  orientation  of  the  side  chains.  Thus,  if  there  be  two, 
dilute  nitric  acid  and  potassium  permanganate,  oxidise  only  one  side  chain, 
while  chromic  acid  oxidises  both,  unless  they  be  in  the  or^o-position  to  one 
another,  when  the  compound  is  either  not  attacked  or  destroyed.  Some- 
what the  same  applies  to  nuclear  substituted  benzenes  with  one  side  chain  ; 
the  or^o-compound  is  often  unattacked  or  destroyed,  whereas  the  para- 
and  meta-compounds  yield  the  corresponding  acids.  Nitro  groups  in  the 
ortho-position  hinder  oxidation  ;  with  halogen  groups  the  meta-compound 
is  least,  and  the  para  most  readily  attacked.  The  methods  for  the 
employment  of  the  various  reagents  mentioned  will  be  clear  from  the 
following  preparations.  Particular  attention  should  be  paid  to  the 
method  of  oxidation  of  the  side  chains  in  phenols  and  amines.  Before 
such  oxidation  can  be  carried  out  these  substituting  groups  have  to  be 
protected,  the  phenol  by  forming  its  sulphuric  or  phosphoric  acid  ester, 
the  amine  by  benzoylation  or  acetylation.  For  the  protected  amides, 
potassium  permanganate  in  presence  of  magnesium  sulphate  is  used  : 
alkaline  permanganate  is  the  best  oxidising  agent  for  phenol  esters. 
Peepakation  182. — Mesitylenic  Acid  (s-Dimethyl-benzoic  acid). 

CeH8.(CH8)a(COOH)[1.3.5].       C9H10O2.  150. 

Uvitic  Acid  (l-Methyl-3-5-dicarboxyl-benzene). 

C6H3(CH3)(COOH)2(l  :  3  :  5).       C9H804.  180. 

20  gms.  (1  mol.)  of  mesitylene  are  refluxed  with  80  gms.  (excess)  of 
30%  nitric  acid  in  a  250-c.c.  round-bottomed  flask,  on  a  sand  bath  in  a 
fume  cupboard  for  18  hours.  The  white  residue  is  filtered  off  on  cooling, 
washed  with  cold  water,  dissolved  in  sodium  carbonate  solution, 
unattacked  mesitylene  and  nitromesitylene  separated,  and  the  mixed  acids 
reprecipitated  by  acidification  with  dilute  hydrochloric  acid.  The  white 
precipitate  is  filtered  off,  washed  with  cold  water,  and  heated  on  a  water 
bath  with  tin  and  excess  of  strong  hydrochloric  acid  for  2  hours  with 
constant  shaking  in  a  capacious  flask  (caution  !  hydrogen  evolved).  Nitro- 
mesitylenic  acid,  a  by-product  in  the  reaction,  is  thus  reduced  and  brought 
into  solution.  On  cooling,  the  undissolved  portion  is  filtered  off,  washed 
with  cold  water,  dissolved  in  dilute  caustic  soda,  and  reprecipitated  from 
the  hot  filtered  solution  with  dilute  hydrochloric  acid.  The  precipitate 
is  a  mixture  of  mesitylenic  and  uvitic  acids.  It  is  filtered  off,  washed  with 
cold  water  and  distilled  in  steam,  till  after  several  hours  no  further  trace 
of  mesitylene  acid  appears  in  the  condenser,  and  the  distillate  ceases 
to  have  an  acid  reaction.  The  greater  portion  of  the  mesitylenic  acid,  v 
free  from  uvitic  acid,  is  suspended  in  the  distillate.    It  is  filtered  off 


OXYGEN  TO  CARBON 


239 


and  the  nitrate  neutralised  with  caustic  soda  solution,  evaporated  to 
small  bulk,  acidified  with  dilute  hydrochloric  acid,  and  the  usually  some- 
what yellow-coloured  acid  thus  obtained  united  to  the  first  portion. 
The  whole  is  redissolved  in  caustic  soda  solution,  filtered  boiling  hot, 
precipitated  by  addition  of  dilute  hydrochloric  acid,  washed  wrEtroold 
water,  and  recrystallised  from  alcohol.  It  is  then  pure  mesitylenic  acid. 
Uvitic  acid  containing  slight  traces  of  mesitylenic  acid  separates  from  the 
residual  liquid  in  the  distilling  flask  on  cooling.  It  is  recrystallised  from 
hot  alcohol,  after  precipitation  by  acid  from  alkaline  solution. 

C6H3(CH3)3  +  30  =  C6H3(CH3)2COOH  +  H20. 
C6H3(CH3)2.COOH  +  30  =  C6H3(CH3)(COOH)2  +  H20. 

Yield. — Mesitylenic  acid  50%  theoretical  (12  gms.).  Uvitic  acid  40% 
theoretical  (12  gms.).  Mesitylenic  acid  forms  colourless  monoclinic 
crystals  ;  difficultly  soluble  in  hot  water  ;  easily  soluble  in  cold  alcohol  ; 
M.P.  166°.  Uvitic  acid  forms  colourless  fine  needles  ;  insoluble  in  cold 
and  hot  water  ;  readily  soluble  in  alcohol  and  ether  ;  M.P.  287° — 288°. 
(A.,  122,  184  ;  141,  144  ;  147,  292  ;  Z.  Ch.,  4,  119.) 

The  above  illustrates  the  action  of  nitric  acid  in  only  oxidising  one  or 
two,  and  not  all  of  the  alkyl  groups  present,  unless  the  heating  be  very 
r>rolonged.  In  the  next  preparation  Method  I.  shows  how  chromic  acid 
or  alkali  bichromate  and  sulphuric  acid  completely  oxidises  all  the  side 
chains  present ;  Method  II.  indicates  how  to  oxidise  completely  the 
partially  oxidised  compound,  potassium  permanganate  being  sufficient. 

Preparation  183. — Terephthalic  Acid  (1 :  4-Benzene-dicarboxylic  acid). 

C6H4(C00H)2[1  :  4].       C8H604.  166. 

Method  I.  (from  ^-xylene). — 20  gms.  (1  mol.)  of  ^-xylene  are  refluxed 
for  24  hours  with  80  gms.  (excess)  of  sodium  or  potassium  bichromate 
and  250  gms.  of  50%  sulphuric  acid.  The  unoxidised  hydrocarbon  is 
removed  by  distillation  in  steam,  and  the  cooled  solution  filtered.  The 
precipitate  is  purified  by  reprecipitation  with  acid  from  its  dilute  solution 
in  sodium  carbonate  or  caustic  alkali. 

C6H4(CH3)2[1  :  4]  ->  C6H4(C00H)2[1  :  4]. 

Yield.— 90%  theoretical  (28  gms.).    (A.,  133,  41.) 

Method  II.  (from  j9-toluic  acid). — 10  gms.  (1  mol.)  of  jo-toluic  acid 
(see  p.  233)  dissolved  in  600  c.cs.  (excess)  of  1%  caustic  soda  solution 
are  refluxed  on  a  water  bath,  and  5%  aqueous  potassium  permanganate 
solution  added  until  the  red  colour  of  the  permanganate  solution  persists 
on  boiling  ;  for  this  about  500  c.cs.  of  potassium  permanganate  solution 
will  be  required.  Excess  of  permanganate  is  destroyed  either  by  adding 
alcohol  until  the  liquid  is  colourless,  the  alcohol  being  oxidised  to  acetalde- 
hyde  or  acetic  acid,  or  sulphur  dioxide  is  bubbled  through  the  warm 
solution  until  all  the  manganese  dioxide  precipitated  during  the  reaction 
dissolves.  In  the  former  method  terephthalic  acid  is  then  precipitated 
after 'filtering  off  the  manganese  dioxide  by  addition  of  cone,  hydrochloric 


240 


SYSTEMATIC  OKGANIC  CHEMISTRY 


acid  at  the  boiling  point,  in  the  latter  terephthalic  acid  is  precipitated  by 
the  sulphur  dioxide  during  the  removal  of  excess  of  permanganate.  In 
both,  the  acid  is  filtered  from  the  cooled  reaction  mixture,  well  washed 
with  cold  water,  and  dried  on  a  water  bath.  It  is  purified  by  reprecipita- 
tion  with  acid  from  an  alkaline  solution. 

CH3.C6H4.COONa  +  NaOH  +  2KMn04 

=  C6H4(COONa),  +  2KOH  +  Mn02  +  2H20. 

Yield. — 90%  theoretical  (12  gms.).  Colourless  crystals  ;  insoluble  in 
water  and  in  alcohol ;  sublimes  without  melting  at  300°.    (A.,  137.  308.) 

The  next  preparation  proves  how,  even  when  two  side  chains  form  part 
of  a  ring,  the  oxidation  follows  the  same  course,  and  an  or$o-dicarboxyli< 
acid  is  obtained.    The  oxidising  agent  used  will  be  noted  ;  it  is  more 
or  less  unique  to  this  reaction. 

Preparation  184.— Phthalic  Acid  (1 :  2-Dicarboxy-benzene). 

C6H4(COOH)2[l  :  2].        C8H604.  166. 

(This  preparation  must  be  carried  out  in  a  good  fume  cupboard.) 

20  gms.  (1  mol.)  of  naphthalene,  15  gms.  of  mercuric  sulphate,  and 
350  gms.  (excess)  of  cone,  sulphuric  acid  are  heated  in  a  retort  with  its 
neck  sealed  to  an  air  condenser  acting  as  a  reflux  until  all  the  naphthalene 
is  dissolved.  The  retort  is  then  lowered  so  that  the  air  condenser  slopes 
downwards  and  delivers  into  a  receiver,  cooled  in  water  and  containing 
200  c.cs.  of  cold  water.  The  contents  of  the  retort  are  heated  cautiously 
at  first,  and  then  vigorously  at  300°  until  the  residue  in  the  retort  is  nearly 
dry.  Unchanged  naphthalene,  phthalic  acid  and  anhydride,  carbon 
dioxide,  sulphur  dioxide,  and  water  all  distil.  The  distillate  is  filtered, 
the  precipitate  well  washed  with  cold  water,  dissolved  in  caustic  soda, 
filtered  from  unchanged  naphthalene,  reprecipitated  by  acidification  with 
hydrochloric  acid,  and  crystallised  from  water,  or  aqueous  alcohol. 

C10H8  +  9H2S04  =  C6H4(COOH)2  +  2C02  +  9S02  +  10H2O. 

Yield. — 60%  theoretical  (16  gms.).  Colourless  plates  slightly  soluble 
in  cold  water  ;  soluble  in  alcohol  and  hot  water  ;  sublimes  on  heating 
to  give  phthalic  anhydride  (long  needles  ;  M.P.  128°).    (D.R.P.,  91202.) 

Mercuric  sulphate  is  used  as  a  catalyst  in  the  above  oxidation,  which 
is  carried  out  on  a  large  scale  in  the  industrial  preparation  of  indigo. 
Sulphuric  acid  may  be  looked  upon  as  a  carrier  of  the  oxygen  of  the  air, 
since  in  practice  the  sulphur  dioxide  evolved  is  reconverted  to  sulphuric 
acid  by  the  contact  process.  The  following  two  preparations  illustrate 
the  oxidation  of  side  chains  in  phenols  and  purines  respectively. 

Preparation  185. — ^-Hydroxy  Benzoic  Acid  (l-Hydroxyl-4-carboxyl 
benzene). 

C6H4(OH)(COOH)[l  :  4].       CvH603.  138. 

10  gms.  (1  mol.)  of  p-cresol  are  dissolved  in  the  minimum  quantity  of 
water,  and  the  solution  heated  at  70°  for  10  hours  with  15  gms.  (excess) 
of  potassium  pyrosulphate.  The  crude  potassium  j?-cresyl  sulphate 
formed  is  heated  on  a  water  bath  with  25  gms.  (excess)  of  potassium 


OXYGEN  TO  CARBON 


241 


hydroxide  dissolved  in  20  c.cs.  of  water,  and  30  gms.  (excess)  of  potassium 
permanganate  in  750  c.cs.  water  gradually  added.  The  whole  is  heated 
for  6  hours.  Sulphur  dioxide  is  then  passed  through  the  mixture  to 
remove  excess  of  permanganate,  and  the  whole  filtered  hot.  The 
filtrate  is  then  boiled  and  acidified  with  hydrochloric  acid,  and  heated  to 
hydrolyse  the  sulphuric  ester.  On  cooling,  the  acid  crystallises  out,  the 
remainder  being  obtained  by  extracting  with  ether.  It  is  recrystallised 
from  ether. 

C6H4OH.CH3  +  2KMn04->C6H4OHCOOH  +  2Mn02  +  2KOH. 

Yield. — 90%  theoretical  (12  gms.).    Colourless  crystals  ;   soluble  in 
hot  water  and  in  ether  ;  M.P.  210°.    (B.,  19,  705.) 
Preparation  186. — Anthranilic  Acid  (l-Amino-2-carboxyl-benzene). 

C6H4(NH2)(COOH)[l  :  2].       C7H702N.  137. 

20  gms.  (1  mol.)  of  acet-o-toluidide  (cf.  Preparation  271)  and  50  gms. 
(excess)  of  magnesium  sulphate  crystals  are  dissolved  in  2 \  litres  of  water, 
the  mixture  heated  to  80°,  and  60  gms.  (excess)  of  solid,  finely  powdered, 
potassium  permanganate  are  added  with  mechanical  stirring ;  this  is 
continued  for  2  hours,  during  which  the  temperature  is  maintained 
at  85°.  Excess  of  permanganate  is  removed  by  the  addition  of 
alcohol,  the  hot  solution  filtered,  and  the  filtrate  acidified  with 
dilute  sulphuric  acid.  The  acetanthranilic  acid  precipitated  is  purified 
by  reprecipitation  from  alkaline  solution  (M.P.  185°),  It  is  hydrolysed 
to  anthranilic  acid  by  boiling  with  excess  of  dilute  hydrochloric  acid  ; 
dilute  alkali  can  also  be  employed.  The  acid  is  recrystallised  from  hot 
water. 

C6H4(NH.CO.CH3)(CH3)[l  :  2]  +  2KMn04  =  C6H4(NHCOCH3)(COOH)[l  :  2] 

+  2Mn02  +  2KOH. 
2KOH  +  MgS04  =  Mg(OH)2  +  K2S04. 

H20 

C6H4(NHCOCH3)(COOH)[l  :  2]  >  C6H4(NH2)(COOH)[l  :  2]. 

Yield. — 80%  theoretical  (15  gms.).  Colourless  crystals  ;  soluble  in 
-  water  and  in  alcohol ;  sublimes  on  heating  ;  M.P.  145°.    (D.R.P.,  94629.) 

Reaction  CI.  (a)  Oxidation  of  Primary  Alcohols  to  the  corresponding 
Carboxylic  Acids.  (A.,  106,  79,  95;  120,  226  ;  B.,  9,  1902  ;  C.  (1907),  1, 
1179.) — The  primary  alcohols  are  readily  oxidised  through  the  corre- 
sponding aldehyde  to  carboxylic  acids  containing  the  same  number  of 
carbon  atoms. 
I  K.CH2OH  ->  R.CHO  ->  R.COOH. 

Chromic  acid  or  alkali  dichft>mate  and  sulphuric  acid  is  employed  for 
the  simpler  alcohols  ;  polyhydric  alcohols  are  usually  oxidised  with 
moderately  dilute  nitric  acid  ;  if  the  acid  be  too  concentrated  the  molecule 
may  be  attached  as  a  whole  (cf.  Preparation  181). 

Preparation  187. — Acetic  Acid  (Ethan-acid). 

CH3COOH.       C2H402.  60. 
To  80  gms.  (excess)  of  finely  powdered  potassium  or  sodium  dichromate, 

S.O.C.  li 


242  SYSTEMATIC  ORGANIC  CHEMISTRY 


and  100  gms.  of  50%  sulphuric  acid  placed  in  a  reflux  apparatus  (see  p.  206), 
70  gms.  (1  mol.)  of  25%  alcohol  are  slowly  added.  The  mixture  is  heated 
for  30  minutes  and  distilled  until  only  very  little  acid  passes  over.  The 
distillate  is  neutralised  with  caustic  potash,  and  evaporated  to  dryness 
on  a  water  bath.  The  residue  is  powdered  and  distilled  with  cone, 
sulphuric  acid  to  139°,  and  the  distillate  fractionated  between  115c 
and  120°. 

3C2H5OH  +  2K2Cr207  +  8H2S04  =  3CH3COOH  +  2K2S04 

+  2Cr2(S04)3  +  11H20. 

Yield. — 80%  theoretical  (18  gms.).  Colourless  liquid  or  crystals ; 
pungent  odour  ;  miscible  with  water  ;  M.P.  16-7°  ;  B.P.  119°  ;  D.  y  1-055. 
(C.  (1907),  I.,  1179.) 

Preparation  188. — Glyceric  Acid  (2  :  3-Di-ol-propan-acid). 

OH.CH2.CH(OH).COOH.       C3H604.  106. 

50  gms.  (1  mol.)  of  glycerol  diluted  with  an  equal  volume  of  water  are 
treated  in  a  tall  narrow  glass  cylinder  with  50  gms.  (excess)  of  90%  nitric 
acid,  the  latter  being  carefully  run  in  below  the  surface  of  the  glycerol 
from  a  funnel,  the  neck  of  which  is  drawn  out  into  a  fine  tube,  so  that 
two  layers  are  formed.  The  whole  is  allowed  to  stand  at  the  ordinary 
temperature,  till  after  some  little  time  the  liquid  becomes  homogeneous. 
The  contents  of  several  (six)  such  cylinders  are  slowly  evaporated  on  a 
water  bath  to  a  syrup,  2  litres  of  water  are  added,  and  the  solution  (a) 
neutralised  with  lead  carbonate  and  a  small  quantity  of  lead  oxide. 
Towards  the  end  of  the  operation  the  liquid  is  boiled  and  filtered  hot. 
Crude  lead  gly cerate  separates  on  concentrating  and  cooling  the  filtrate. 
The  salt  is  detached  by  warming  from  the  sides  of  the  vessel,  to  which  it 
adheres  firmly.  A  second  crop  of  crystals  slowly  separates  on  concen- 
trating the  mother  liquors.  The  finely  powdered  salt  made  into  a  paste 
with  water  is  treated  with  hydrogen  sulphide  in  2-5  gm.  lots,  and  the 
solution,  filtered  from  lead  sulphide,  evaporated  on  a  water  bath,  when 
the  acid,  remains  as  a  thick  syrup. 

The  aqueous  solution  (a)  may  also  be  worked  up  for  glyceric  acid  by 
boiling  it  with  excess  of  calcium  carbonate  and  filtering  hot.  The  calcium 
gly  cerate,  which  separates  on  cooling  and  concentrating,  is  recrystalfised 
from  hot  water,  suspended  in  water,  and  decomposed  by  treatment  with 
the  theoretical  quantity  of  oxalic  acid  determined  by  estimating  the 
calcium  by  ignition  in  a  sample  of  the  salt.  The  clear  solution  filtered 
from  calcium  oxalate  is  evaporated  as  above. 

(OH)CH2.CH(OH)CH2(OH)  +  02  =  (OH)CH2CH(OH)COOH  +  H20. 

Yield. — 80%  theoretical  (275  gms.  from  300  gms.  of  glycerol).  Strongly 
acid  syrup,  faintly  yellow  colour  ;  has  never  been  crystallised  ;  soluble 
in  water,  alcohol  and  acetone  ;  insoluble  in  ether ;  decomposes  on 
boiling.    (A.,  106,  79,  95  ;  120,  226  ;  B.,  9,  1902.) 

Reaction  CI.  (b)  Oxidation  of  Aldehydes  to  Carboxylic  Acids.  (B.,  17, 
1298  ;  24,  521  ;  A.,  227,  224.)— The  aldehydes  are  very  readily  oxidised 


OXYGEN  TO  CARBON 


243 


to  the  corresponding  acids ;  in  the  oxidation  of  primary  alcohols  to 
acids,  it  is  the  first  stage  which  is  the  more  difficult  to  achieve.  A  great 
variety  of  oxidising  agents  may  be  employed — nitric  acid  is  used  for  the 
less  complex  aldehydes  ;  in  the  sugar  group,  where  the  reaction  is  of 
importance  (see  below),  bromine  gives  very  good  results. 

E.CHO  +  0  =  R.COOH. 

Preparation  189. — Gluconic  Acid  (Pentol-hexan  acid  -|  1 — \-). 

COOH 
H.C.OH 

HhJ'.oh       c«h"°"  196' 

H.C.OH 
CH2OH. 

50  gms.  (1  mol)  of  glucose  dissolved  in  400  c.cs.  of  water  are  treated  in 
a  stoppered  bottle  with  100  gms.  (excess)  of  bromine.  The  mixture  is 
allowed  to  stand,  with  frequent  shaking,  for  3  days  at  ordinary  tempera- 
tures, and  then  boiled  in  a  porcelain  dish  in  a  fume  cupboard  with  constant 
stirring,  until  all  the  bromine  has  disappeared.  The  solution  is  cooled, 
diluted  with  water  to  500  c.cs.,  and  neutralised  with  lead  carbonate  sus- 
pended in  water.  The  precipitate  is  filtered  at  the  pump,  suspended  in 
water  and  saturated  with  hydrogen  sulphide,  filtered  and  neutralised 
by  boiling  for  J  hour  with  precipitated  chalk.  The  filtrate  is  evaporated 
to  about  100  c.cs.  and  seeded  in  the  cold  with  a  crystal  of  calcium 
gluconate.  After  24  hours  the  whole  is  filtered  at  the  pump  and  the 
precipitate  washed  with  cold  water,  redissolved  in  a  small  quantity  of 
hot  water,  and  boiled  with  addition  of  animal  charcoal.  The  latter  is 
filtered  off  and  the  solution  treated  with  the  exact  quantity  of  oxalic  acid 
in  aqueous  solution  necessary  to  precipitate  the  calcium  present,  a 
portion  of  the  precipitate  obtained  above  being  ignited  and  the  calcium 
in  it  estimated  for  the  purpose.  The  precipitated  calcium  oxalate  is 
filtered  off  and  washed,  and  the  washings  and  filtrate  evaporated  to  a 
syrup  on  a  warm  water  bath  under  reduced  pressure. 

C5Hn05CHO  +  H20  +  Br2  =  C5Hn05COOH  +  2HBr. 

Yield. — 50%  theoretical  (30  gms.).  Acid  syrup  ;  has  never  been 
crystallised  ;  soluble  in  water  ;  on  standing  or  heating  changes  in  part  to 
a  crystalline  lactone  ;  M.P.  130°— 135°.    (B.  17,  1298.) 

This  preparation  is  important  in  the  sugar  group,  as  it  is  possible  to 
pass  from  one  stereoisomeric  acid  to  another  by  heating  with  pyridine — 
this  enables  the  corresponding  sugars  to  be  transformed  one  into  another 
by  oxidation  to  the  acid,  transformation  of  the  acid  to  its  stereoisomer, 
and  reduction  of  the  lactone  of  the  latter  acid  (see  p.  184). 

Preparation  190. — Saccharic  Acid  (Tetrol-hexan-diacid  -\  h  +). 

COOH.(CHOH)4.COOH.       C6H10O8.  210. 
50  gms.  (1  mol)  of  anhydrous  glucose  are  heated  in  a  dish  on  a  water 

R  2 


244  SYSTEMATIC  ORGANIC  CHEMISTRY 


bath  with  350  gms.  (excess)  of  25%  nitric  acid  and,  while  stirred  mechani- 
cally, are  evaporated  to  a  syrup,  which  is  dissolved  in  a  little  water,  and 
again  evaporated.  Should  the  mass  begin  to  show  the  slightest  sign  of 
charring,  heating  is  immediately  discontinued.  The  whole  is  dissolved  in 
200  c.cs.  of  water,  and  neutralised  with  a  saturated  solution  of  potassium 
carbonate.  25  c.cs.  of  50%  acetic  acid  are  added  and  the  liquid  evaporated 
to  about  75  c.cs.  On  frequent  rubbing  and  long  standing  in  the  cold,  acid 
potassium  saccharate  crystallises  out,  and  is  filtered  at  the  pump  after  a 
further  12  hours  standing,  washed  with  a  very  little  cold  water,  and 
recrystallised  from  hot  water  with  addition  of  animal  charcoal ;  if  not 
quite  colourless,  the  operation  is  repeated.  The  salt  is  treated  with  excess 
of  10%  hydrochloric  acid  and  evaporated  on  a  warm  water  bath  under 
reduced  pressure  to  a  deliquescent  mass,  which  is  treated  with  absolute 
alcohol,  filtered,  and  the  nitrate  evaporated  under  reduced  pressure  till 
all  the  alcohol  is  removed. 

CH„OH  COOH 


)H)4  >  (CHOH)4 


'CI 

I 

CHO  COOH. 


Yield. — 20%  theoretical  (12  gms.).  Colourless  deliquescent  mass  ; 
soluble  in  water ;  very  soluble  in  alcohol  ;  changes  on  standing  to  a 
crystalline  lactone  (M.P.  131°).    (B.,  24,  521.) 

This  preparation  illustrates  the  oxidation  to  a  carboxylic  acid,  both  of 
a  primary  alcohol  and  an  aldehyde.  The  reaction  also  is  of  im- 
portance in  the  sugar  group,  for  it  is  possible  to  reduce  the  carboxyl  group 
in  saccharic  acid  which  comes  from  the  aldehyde  group,  to  a  primary 
alcohol  group  while  the  carboxyl  corresponding  to  the  primary  alcohol 
group  is  reduced  to  an  aldehyde.  In  this  way  a  new  sugar  stereoisomeric 
with  the  first  may  be  obtained. 

Following  is  one  of  the  applications  of  the  method — 

(+-  +  +)  >  (+-  +  +)  — M+  -  +  +)  or  (  +  •+  -  +) 

Glucose  Gluconic  acid  Saccharic  acid  > 


(+  +  -+)         (+  +  -+) 
Gulonic  acid  >  Gulose. 

The  next  preparation  illustrates  the  hydrolysis  of  a  di-saccharose,  and 
the  simultaneous  oxidation  of  the  mono-saccharoses  so  formed. 
Preparation  191. — Mucic  Acid  (Tetrol-hexan-diacid  -\  \-). 

COOH 
H.C.OH 
OH.C.H 

OH.C.H  b6n10U8I  ZAU- 

H.C.OH 
COOH 


OXYGEN  TO  CARBON 


245 


100  gms.  (1  mol.)  of  lactose  are  heated  on  a  water  bath  with  1,500  gms. 
(excess)  of  25%  nitric  acid,  the  whole  being  continuously  stirred,  until  the 
volume  is  reduced  to  250  c.cs.  The  cooled  acid  mass  is  diluted  with 
750  c.cs.  of  water,  filtered  at  the  pump,  well  washed  with  cold  water,  and 
dissolved  in  just  sufficient  N/1  caustic  soda  solution  (excess  tends  to 
repreeipitate  the  sodium  salt).  The  latter  solution  is  warmed  with  animal 
charcoal  and  filtered,  and  the  acid  reprecipitated  by  addition  of  the 
equivalent  in  5N  hydrochloric  acid  of  the  N/1  caustic  soda  used  for 
solution.  During  this  addition  the  temperature  must  not  rise  above  15°, 
otherwise  the  lactone  of  the  acid  may  be  formed.  The  whole  is  kept  for 
12  hours  in  a  freezing  mixture,  and  the  precipitate  filtered  at  the  pump, 
well  washed  with  cold  water  and  dried  on  a  water  bath. 

C12H22OH  +  H20  =  C6H1206  +  C6H1206. 
Lactose.  Glucose.  Galactose. 

_02 

C6H1206        >  C6H10O8. 
Glucose.  Saccharic  acid. 

_02 

C6H1206        >  C6H10O8. 
Galactose.  Mucij  acid. 

Saccharic  acid  being  soluble  in  water  remains  in  solution. 

Yield. — 55%  theoretical  (32  gms.).  White  crystalline  powder  ;  almost 
insoluble  in  cold  water  and  in  alcohol ;  M.P.  210°  (with  decomposition). 
(A,  227,  224.) 


CHAPTER  XVII 


oxygen  to  carbon 
Oxide-Oxy  Compounds 

Esters  and  Acid  Anhydrides 

This  section  deals  first  with  the  preparation  of  alkyl-acyl  oxide  com- 
pounds— esters — by  the  interaction  of  an  acid  or  an  acid  derivative  and 
an  alcohol.  The  various  methods  used  all  have  their  origin  in  the  fact 
that  the  formation  of  an  ester  and  water  from  a  mixture  of  an  acid  and  an 
alcohol  is  a  reversible  reaction,  and  special  measures  have  to  be  adopted 
to  displace  the  equilibrium  towards  the  complete  formation  of  ester. 

The  second  portion  of  the  section  discusses  the  preparation  of  di-acyl 
oxide  compounds — acid  anhydrides. 

Reaction  CII.  Direct  Action  of  an  Acid  on  an  Alcohol.  (A.  Ch.,  58,  44.) 
— Few  normal  esters  are  prepared  in  this  way — dimethyl  oxalate  being 
an  exception  ;  in  this  case  the  water  formed  is  probably  prevented  from 
inducing  the  back  reaction  by  the  presence  of  anhydrous  oxalic  acid — even 
so,  the  yield  is  only  40%.  With  acid  esters,  however,  good  yields  can  be 
obtained,  since  only  incomplete  esteriflcation  is  required. 

/COOH  /COOEi 
E.<  +  KiOH  =  E<  +  H20. 

\COOH  \COOH 

Preparation  192. — Di-Methyl  Oxalate  (Di-methyl  ester  of  ethan-diacid). 

COO.CHg 

I  C4H604.  118. 

COO.CH3 

In  order  to  prevent  hydrolysis  of  the  ester  as  it  is  formed,  it  is  necessary 
in  this  preparation  to  use  anhydrous  oxalic  acid  and  to  purify  and  dry  the 
methyl  alcohol  as  described  on  p.  206. 

63  gms.  (1  mol.)  of  oxalic  acid  crystals  are  powdered  and  heated  on  a 
boiling  water  bath  till  no  more  water  is  given  off  (1 — 2  hours),  and  are 
then  heated  in  an  air  oven  at  110° — 120°  until  the  required  loss  in  weight 
(18  gms.)  has  taken  place.  During  the  heating,  the  acid  should  be  pow- 
dered occasionally.  The  anhydrous  acid  is  refluxed  on  a  water  bath  with 
50  gms.  (excess)  of  pure  anhydrous  methyl  alcohol  for  2 J  hours,  excess 
alcohol  removed  on  a  water  bath,  and  the  residue  distilled  to  120°  ; 
the  water  is  run  out  of  the  condenser,  and  the  fraction  160° — 165° 
collected.  The  solid  portion  is  filtered  off,  dried  on  a  porous  plate, 
and  recrystallised  from  methyl  or  ethyl  alcohol. 

246 


OXYGEN  TO  CARBON 


247 


COOH 

|  +  2CH3.OH  =  j         <  +  2H20. 

COOH  COOCH3 

Yield. — 40%  theoretical  (25  gms.).  Colourless  crystalline  plates  ; 
somewhat  soluble  in  alcohol ;  M.P.  54°  ;  B.P.  163°.    (A.  Ch.,  58,  44.) 

In  the  next  preparation  the  forward  reaction  is  assisted  by  removal  of 
the  ester  as  fast  as  it  is  produced  (cf.  Reaction  CIIL).  This  is  only 
possible  when  a  strong  acid  is  present  to  act  as  a  catalyst— the  hydrogen 
ions  cause  fresh  ester  rapidly  to  be  formed  (see  also  under  Reaction 
CVIL).  It  is  necessary  that  the  ester  should  be  volatile,  or  in  some 
other  manner  readily  removable  from  the  sphere  of  the  reaction. 

Preparation  193.— Ethyl  Nitrate  (Ethyl-ester  of  nitric  acid). 

CH3.CH2.O.N02.       C2H503N.  91. 

To  20  gms.  (1  mol.)  of  cold  "  boiled-out "  67%  nitric  acid,  2  gms.  of  urea 
in  15  gms.  (excess)  of  absolute  alcohol  are  added,  and  half  of  the  mixture 
distilled  off  on  a  water  bath  in  a  tubulated  retort  attached  to  condenser 
and  receiver.  40  gms.  of  similar  nitric  acid  mixed  with  30  gms.  of  absolute 
alcohol,  and  containing  0-5  gm.  of  urea,  are  now  allowed  to  drop  in 
through  the  tubulus  from  a  tap-funnel  at  the  same- rate  as  the  liquid 
distils.  Water  is  added  to  the  distillate,  the  ester  which  separates  is 
washed  several  times  with  cold  water,  dried  over  calcium  chloride,  and 
distilled  from  a  water  bath,  the  fraction  84° — 88°  being  retained.  Care 
must  be  taken  in  this  experiment,  as  the  ester  is  liable  to  explode  when 
quickly  heated.  All  operations  should  be  carried  out  behind  a  metal 
screen. 

C2H5OH  +  HNO3  =  C2H5N03  +  H20. 

Yield. — 75%  theoretical  (22  gms.).  Colourless  liquid  ;  characteristic 
odour  ;  liable  to  explode  when  quickly  heated  ;  B.P.  86°  ;  D.  x45  1-112. 

Urea  is  used  above  to  decompose  any  nitrous  acid  formed,  as  the 
presence  of  the  latter  tends  to  cause  explosion. 

CO(NH2)2  +  2HN02  =  C02  4-  2N2  +  3H20. 

(C.  (1903),  II.,  338  ;  B.,  14,  421.) 

The  following  illustrates  the  preparation  of  acid  esters. 

Preparation  194. — Ethyl  Hydrogen  Tartrate  (Monoethyl  ester  of  di- 
hydroxy-butan  diacid). 


CH(OH).COOH 

I 

CH(OH).COOC2H5 


C6H10O6.  178. 


20  gms.  (1  mol.)  of  finely  powdered  tartaric  acid  and  30  gms.  (excess)  of 
absolute  alcohol  are  heated  for  6  hours  at  70°  on  a  water  bath  in  a  reflux 
apparatus.  An  equal  volume  of  water  and  then  an  excess  of  powdered 
barium  carbonate  are  added,  and  the  liquid  filtered  from  barium  tartrate 
and  excess  of  barium  carbonate.  The  filtrate  is  evaporated  to  crystal- 
lisation on  a  water  bath,  cooled,  and  the  crystals  of  barium  ethyl-tartrate 
which  separate  filtered  off  at  the  pump  and  dried  on  a  porous  plate. 


248 


SYSTEMATIC  ORGANIC  CHEMISTRY 


They  are  weighed  and  treated  with  the  theoretical  amount  of  2N  sulphuric 
acid  to  precipitate  the  barium  present,  barium  sulphate  is  filtered  off,  and 
the  nitrate  evaporated  to  crystallisation  point.  The  crystals  which 
separate  are  recrystallised  from  a  little  water. 

CH(OH)COOH  CH(OH)COOC2H5 

I  +  C2H5.OH  =  |   •  +HoO, 

CH(OH)COOH  CH(OH)COOH 

Yield. — 70%  theoretical  (17  gms.).  Colourless  crystals  ;  somewhat 
soluble  in  water  ;  M.P.  90°.    (A.,  22,  248.) 

By  a  repetition  of  the  above  process,  using  the  alkyl  hydrogen  tartrate, 
di-ethyl  tartrate  can  be  obtained  but  the  yield  is  poor. 

When  cone,  sulphuric  acid  acts  on  the  alcohols,  the  acid  esters  only  are 
formed,  though  sulphuric  acid,  by  its  great  affinity  for  water,  promotes 
almost  complete  esterification  in  other  instances  (see  Reaction  CVII.)  ; 
for  the  preparation  of  normal  sulphuric  esters,  see  Preparation  207. 

Reaction  CIII. — Continual  removal  of  Water  in  a  suitable  Apparatus. 
(P.  R.  S.,  25,  831  ;  J.  C.  S.,  87,  1657.)— In  this  method,  which  requires 
little  elaboration,  it  is  necessary  that  the  acid  and  ester  have  high  boiling- 
points  compared  with  that  of  water.  The  latter  is  continually  volatilised 
with  the  alcohol  and  circulated  over  a  dehydrating  agent  which  absorbs 
it — the  alcohol  being  returned  to  the  reaction  vessel. 

Prepaeation  195. — Di-ethyl  Tartrate  (Di-ethyl  ester  of  di-hydroxy- 
butan-diacid). 

CH(OH)COOC2H5 

I  C8H1406.  206. 

CH(OH)COOC2H5. 

Method  I. — The  apparatus  described  in  Preparation  1  is  fitted  up,  a 
500-c.c.  flask  being  used,  and  30  gms.  (1  mol.)  of  finely  powdered  tartaric 
acid,  150  gms.  (excess)  of  absolute  alcohol,  and  50  gms.  of  crystallised 
benzene  are  placed  in  the  flask.  The  object  of  the  benzene  is  to  help  to 
volatilise  the  water  produced  by  forming  with  it  and  the  alcohol  the  low 
boiling  ternary  system — alcohol-benzene-water.  The  iron  tube  is  packed 
with  small  lumps  of  good  quicklime,  and  is  heated  to  a  temperature  of  90°. 
The  mixture  in  the  flask  is  boiled,  a  few  pieces  of  porous  porcelain  being 
added  to  promote  steady  ebullition.  Esterification  proceeds  almost  to 
completion,  owing  to  the  removal  by  the  quicklime  of  the  water  formed. 
After  6  hours,  the  liquid  in  the  flask,  which  will  have  become  quite  viscid 
owing  to  the  formation  of  the  ester,  is  distilled  on  a  water  bath  until  all 
the  benzene  and  excess  of  alcohol  have  been  removed  ;  the  residue  is 
fractionated  from  a  metal  bath  under  reduced  pressure. 

Yield.— 90%  theoretical  (37  gms.).  (P.  R.  S.,  25,  831  ;  J.  C.  S.,  87, 
1657.) 

Method  II. — The  apparatus  (Fig.  46)  is  fitted  up,  being  held  in  position 
by  a  clamp  holding  the  condenser  C.  In  the  flask  A  are  placed  150  gms.  of 
tartaric  acid  (or  other  acid  to  be  esterified),  which  need  not  be  specially 
dried  or  powdered,  and  which  is  just  covered  with  alcohol.  B  contains 
140  gms.  (3  mols.)  of  the  latter,  and  100  gms.  of  fresh  potassium  carbonate 


OXYGEN  TO  CARBON 


249 


or  other  suitable  solid  desiccating  agent.  The  apparatus  communicates 
with  the  open  air  only  by  means  of  the  tube  E.  A  is  immersed  to  the  neck 
in  an  oil  bath  which  is  slowly  heated  to  130°,  and  as  soon  as  most  of  the 
alcohol  in  it  has  distilled  into  B,  the  latter  is  heated  on  a  boiling  water  bath. 
The  alcohol  in  B  passes  up  the  fractionating  column  D,  which  assists  the 
action  of  the  dehydrating  agent,  and  into  A  whence  what  does  not  combine 
with  the  acid,  and  the  water  formed  in  the  esterification,  distil  into  B. 
After  10  hours,  the  excess  of  alcohol  is  distilled  off  from  A,  and  the  residue 
fractionated  from  a  metal  bath  under  reduced  pressure. 
Yield.— 80%  theoretical  (165  gms.).    (J.  C.  S.,  79,  517.) 

(CH(OH)COOH)2  +  2C2H5OH  =  (CH(OH)COOC2H5)2  +  2H20. 

Colourless  viscid  liquid  ;  insoluble  in  water  ;  miscible  with  alcohol ; 
B.P.  11  155°  ;  B.P.  28  164°  ;  D.  2  1-072. 

Di-methyl  tartrate  (B.P. 760  280°  ;  D.  1-34)  is  prepared  in  an  exactly 
similar  manner. 

Reaction  CIV.  Use  of  Concentrated  Sulphuric  Acid  or  of  Hydrogen 
Chloride  to  promote  Esterification.  (B.,  13,  1176  ;  28,  1150,  3252  ;  Phil. 
Trans.,  156,  37  ;  BL,  33,  350  ;  J.,  (1874),  352  ;  A.,  204,  126.)— Cone, 
sulphuric  acid  being  a  dehydrating  agent  is  frequently  used  to  promote 
esterification  ;  it  also  acts  as  a  catalyst  increasing  the  speed  of  the  reaction, 
though  in  so  doing  it  does  not  change  the  equinbrium  point.  Saturation 
of  the  alcohol  used  with  hydrochloric  acid  has  also  been  employed  with 
the  same  end  in  view,  but  it  has  been  found  that  4%  hydrogen  chloride  in 
the  alcohol  gives  even  better  results.  Hence  it  is  probable  that  this  acid 
acts  catalytically  and  not  as  a  dehydrating  agent. 

Peepaeation  196.— Ethyl  Acetate  (Ethyl  ester  of  ethan  acid). 

CH3.COOC2H5.       C4H802.  88. 

200  c.cs.  of  a  mixture  of  equal  volumes  of  glacial  acetic  acid  (1  mol.),  and 
absolute  alcohol  (1  mol.),  are  added  drop  by  drop  at  the  same  speed  as  the 
liquid  distils,  to  a  mixture  of  50  c.cs.  of  cone,  sulphuric  acid,  and  50  c.cs. 
(excess)  of  absolute  alcohol  in  a  distilling  flask  attached  to  a  condenser 
and  receiver  and  heated  in  a  metal  bath  kept  at  140°.  The  distillate  is 
shaken  in  an  open  tap-funnel  with  aqueous  sodium  carbonate  solution 
until  the  upper  layer  is  no  longer  acid  to  moistened  blue  litmus  paper. 
This  layer  is  shaken  with  50  c.cs.  of  a  50%  aqueous  solution  of  calcium 
chloride  to  remove  alcohol,  and  then  allowed  to  stand  24  hours  in  contact 
with  calcium  chloride.  It  is  filtered  through  a  dry  filter  paper  and 
fractionated  on  a  water  bath,  the  fraction  73° — £0°  being  redistilled. 

CH3COOH  +  C2H5OH  =  CH3COOC2H5  +  H20. 

Yield. — 85%  theoretical  (130  gms.).  Colourless  liquid  ;  characteristic 
odour  ;  somewhat  soluble  in  water  ;  miscible  with  alcohol,  ether  and 
acetic  acid  ;  B.P.  78°  ;  D.  *  0-9068  :  D.  24°  0-900.  (Phil.  Trans.,  156,  37  ; 
BL,  33,  350). 

Methyl  acetate  (B.P.  57°,  D,  f  0-904)  is  prepared  in  a  similar  manner 
from  methyl  alcohol. 


250 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  197. — Di-ethyl  Tartrate  (Di-ethyl  ester  of  butan-diol 
diacid). 

(CH(OH)COOC2H5)2.       C8H1406,  206. 

50  gms.  (1  moL)  of  finely  powdered  tartaric  acid  are  refluxed  on  a  water 
bath  with  150  c.cs.  (excess)  of  absolute  alcohol  until  dissolved,  and  the 
solution  saturated  with  hydrogen  chloride  at  0°  C.  After  12  hours  it  is 
heated  under  reduced  pressure  on  a  water  bath  to  remove  hydrogen 
chloride,  excess  of  alcohol  and  water,  and  the  residue,  which  consists 
chiefly  of  ethyl  hydrogen  tartrate,  treated  with  a  further  150  c.cs.  (excess) 
of  absolute  alcohol,  the  mixture  again  saturated  with  hydrogen  chloride 
at  0°  C,  and  allowed  to  stand  for  12  hours.  It  is  then  fractionated  under 
reduced  pressure,  and  the  fraction,  B.P.  11  152°— 158°  or  B.P.  18-20  159°— 
168°,  refractionated  under  reduced  pressure. 

Yield. — 80%  theoretical  (55  gms.).  Colourless  viscid  liquid  ;  insoluble 
in  water  ;  miscible  with  alcohol ;  B.P.  11  155°  ;  B.P.  23  164°  ;  D.  J  1-072. 
(B.,  13,  1176.) 

The  above  exemplifies  the  old  method  of  saturation  of  the  mixture  with 
hydrogen  chloride  ;  the  Fischer-Speir  modification,  illustrated  in  the 
following  preparation,  can  be  employed  ;  the  time  for  the  preparation  is 
shortened,  and  only  half  the  above  quantity  of  alcohol  is  required. 

Preparation  198. — Ethyl  Benzoate  (Ethyl  ester  of  benzoic  acid). 

C6H5.COOC2H5.       C9H10O2.  150. 

150  gms.  (excess)  of  absolute  alcohol  are  cooled  in  ice,  and  dry  hydrogen 
chloride  bubbled  through  it  until  an  increase  in  weight  of  6  gms.  has  been 
obtained.  50  gms.  (1  mol.)  of  benzoic  acid  are  added,  and  the  whole 
refluxed  for  2  hours  until  on  pouring  a  sample  into  water  no  benzoic  acid 
separates.  The  excess  of  alcohol  is  removed  on  a  water  bath,  the  residue 
diluted  with  2  volumes  of  water,  and  the  whole  shaken  in  an  open  vessel 
with  solid  sodium  carbonate  until  any  acid  present  is  removed.  The 
ester  is  then  extracted  with  ether,  the  extract  dried  for  24  hours  over  pure 
potassium  carbonate  and  fractionated,  the  fraction  204° — 213°  being 
redistilled.  The  carbonate  should  be  made  by  heating  the  bicarbonate, 
in  order  to  ensure  its  being  pure  and  anhydrous. 

C6H5.COOH  +  C2H5OH  =  C6H5COOC2H5  +  H20. 

Yield. — 80%  theoretical  (49  gms.).  Colourless  oil ;  sweetish  odour  ; 
insoluble  in  water;  miscible  with  alcohol  and  ether;  B.P.  700  211°; 
D. l!  1-05  ;  D.  20  1-047.    (B.,  28,  1150.) 

The  above  preparation  can  also  be  performed  using  10  gms.  of  sulphuric 
acid,  100  gms.  of  absolute  alcohol,  and  50  gms.  of  benzoic  acid.  Although 
less  alcohol  is  used,  the  yield  is  90%  theoretical,  being  probably  increased 
by  the  dehydrating  action  of  the  sulphuric  acid.  Methyl  benzoate  (B.P. 
199°)  can  be  prepared  in  a  similar  manner. 

The  following  exemplifies  the  preparation  of  an  ester  by  the  above 
methods,  using  a  salt  of  an  acid  from  which  the  mineral  acid  present 
liberates  the  free  acid.  This  modification  is  especially  useful  when  the 
acid  it  is  required  to  esterify  is  difficult  to  isolate  in  a  free  state. 


OXYGEN  TO  CARBON 


251 


Preparation  199. — Di-ethyl  Malonate  (Di-ethyl  ester  of  propan  diacid). 

CH2(COOC2H5)2.       C7H1204.  160. 

For  this  esterification  250  c.cs.  (excess)  of  absolute  alcohol  are  employed 
to  100  gms.  of  hydrated  calcium  malonate,  which  has  been  dried  as  com- 
pletely as  possible  on  a  water  bath,  or  to  95  gms.  of  the  anhydrous  salt 
of  the  acid.  It  is  better  to  use  the  latter.  20  gms.  of  the  dried  salt 
are  placed  in  a  litre  flask,  all  the  absolute  alcohol  is  poured  on  to  it,  and  a 
stream  of  well-dried  hydrogen  chloride  is  passed  in,  so  that  the  liquid 
becomes  warm.  The  remainder  of  the  calcium  salt  is  added  in  15-gm.  lots 
as  fast  as  the  previous  portion  disappears.  By  this  means  caking  of  the 
calcium  salt  is  prevented.  The  complete  solution  should  take  about 
30  minutes,  by  which  time  the  alcoholic  liquid  will  be  saturated  with 
hydrogen  chloride.  After  standing  for  24  hours,  the  solution  is  evaporated 
to  a  small  volume  under  reduced  pressure,  and  the  residual  ester  dissolved 
in  ether.  The  ethereal  solution  is  dried  over  calcium  chloride,  the  ether 
removed  on  a  water  bath,  and  the  residue  fractionated,  the  fraction  195° — 
198°  being  retained. 

CH2(COO)2Ca  +  2HC1  +  2C2H5OH  =  CH2(COOC2H5)2  +  CaCl2  +  2H20. 

Yield. — 75%  theoretical  (65  gms.).    Colourless  liquid  ;  B.P.  (uncorr.) 
195°  ;  B.P.  (corr.)  197°— 198°  ;  D.  «  1-068.    (A.,  204,  126.) 
Preparation  200. — Amyl  Nitrite  (Amyl  ester  of  nitrous  acid). 

0:N.O.C5Hu.       C5Hn02N.  117. 

30  gms.  (2  mols.)  of  amyl  alcohol  and  20  gms.  (excess)  of  sodium  nitrite 
are  treated  in  a  500-c.c.  round-bottomed  flask  cooled  in  ice,  with  18  gms. 
(excess)  of  cone,  sulphuric  acid  added  drop  by  drop  with  constant  shaking. 
The  addition  must  be  carried  out  in  a  fume  cupboard,  and  care  must  be 
taken  not  to  inhale  the  vapour  of  the  amyl  nitrite.  When  all  the  acid  is 
added,  the  top  layer  of  ester  is  separated  and  the  residue  shaken  with 
water  ;  the  further  quantity  of  ester  which  separates  is  added  to  that 
first  obtained,  and  the  whole  washed  with  water,  separated,  dried  for  24 
hours  over  calcium  chloride  and  distilled,  the  fraction  94° — 101°  being 
redistilled. 

2C5HnOH  +  2NaN02  +  H2S04  =  2C6HuONO  +  Na2S04  +  2H20. 

Yield. — 75%  theoretical  (30  gms.).  Greenish-yellow  liquid  ;  charac- 
teristic odour  ;  insoluble  in  water  ;  miscible  with  ether  and  alcohol ; 
B.P.  760  96°  ;  D.  J  0-902.    (J.,  (1874),  352.) 

Reaction  CV.    Action  of  Acid  Anhydrides  on  Alcohols  and  Phenols. 

(B.,  12,  2059  ;  21,  1172.)— This  method  is  not  greatly  used,  owing  to  the 
acid  anhydrides  not  being  so  readily  obtainable  as  the  acids  themselves 
or  the  acid  chlorides  (see  Reaction  CIX.).  It  is  chiefly  employed  in  the 
preparation  of  the  acetates  of  alcohols  with  the  purpose  of  determining 
the  percentage  of  hydroxyl  present. 

2K1OH  +  (RuCO)20  =  2E-11COOE1  +  H20. 


252  SYSTEMATIC  OKGANIC  CHEMISTRY 


The  esterification  is  brought  about  by  heating  the  alcohol  and  anhydride 
together,  usually  with  the  addition  of  a  dehydrating  agent — e.g.,  fused 
zinc  chloride,  anhydrous  sodium  acetate,  etc.  The  presence  of  alkali 
often  facilitates  the  interaction. 

Preparation  201. — Mannitol  Hexacetate. 

(CH2O.COCH3)(CHO.COCH3)4(CH2O.COCH3).       C18H26012.  434. 

10  gms.  of  mannitol,  10  gms.  of  fused  sodium  acetate,  and  40  gms. 
acetic  anhydride,  are  placed  in  a  small  flask  provided  with  a  reflux  con- 
denser and  heated,  at  some  distance  above  a  wire  gauze,  to  gentle  boiling 
for  an  hour.  The  product  is  poured  into  water,  well  stirred  and  broken 
up  with  a  glass  rod.  After  some  time  it  is  filtered  off,  washed  with  water, 
and  recrystallised  from  alcohol. 

CH2OH(CHOH)4CH2OH  +  3(CH3CO)20  ->  C18H26012  +  3H20. 

Yield. — Almost  theoretical  (24  gms.).  Colourless  crystals  ;  insoluble 
in  water  ;  soluble  in  hot  alcohol ;  M.P.  119°.    (B.,  12,  2059.) 

The  above  preparation  represents  a  general  method  for  the  preparation 
of  acetyl  derivatives  of  hydroxy  compounds.  Fused  zinc  chloride  may  be 
used  in  place  of  fused  sodium  acetate,  but  charring  of  the  product  is  more 
likely  to  occur. 

The  next  preparation  illustrates  the  action  of  the  anhydride  of  a  dibasic 
acid. 

Preparation  202. — Methyl  Hydrogen  Succinate  (Mono-methyl-ester  of 
butan  diacid). 

CH2COOCH3 

|  C5H804.  132. 

CH2COOH. 

10  gms.  (1  mol.)  of  succinic  anhydride  (see  p.  259)  are  refluxed  with 
10  gms.  (excess)  of  pure  methyl  alcohol  (see  p.  206)  for  1  hour,  excess 
of  alcohol  is  removed  under  reduced  pressure  at  ordinary  temperature, 
and  the  residue  recrystallised  from  hot  carbon  disulphide  (Caution  !) 

CH2COx  CH2CO.OCH3 

|  >0  +  CH3OH  =  | 

CH2C(K  CH2CO.OH. 

Yield. — Almost  theoretical  (13  gms.).  Glistening  plates  ; '  insoluble  in 
water  ;  M.P.  57° ;  B.P.  20 151°.    (C,  (1904),  [1],  1484.) 

Phenols  and  naphthols  also  can  be  readily  acetylated,  using  acetic 
anhydride.    The  general  method  is  shown  in  the  next  preparation. 

Preparation  203. — ^-Naphthyl  Acetate  (Acetyl  derivative  of  2-hydroxy- 
naphthalene). 

/\/\O.CO.CH3. 

I      I      I  C12H10O2.  186. 

10  gms.  (1  mol.)  of  /S-naphthol  are  refluxed  for  15  minutes  with  20 
gms.  (excess)  of  acetic  anhydride,  and  the  whole  poured  into  cold  water. 


OXYGEN  TO  CARBON 


253 


The  precipitate  is  filtered  at  the  pump,  washed  with  cold  water,  and 
recrystallised  from  aqueous  alcohol. 

2C10H7OH  +  (CH3CO)20  =  2C10H7O.COCH3  +  H20. 

Yield. — Theoretical  (135  gms.).  Colourless  crystals ;  insoluble  in 
water  ;  M.P.  70°.    (A.,  209,  150.) 

An  example  is  here  given  of  the  reduction  of  an  anthraquinone  to 
its  unstable  dihydroxy-anthracene  derivative,  and  the  simultaneous 
acetylation  of  the  latter  to  form  the  stable  di-acetyl  compound. 

Preparation  204. — Di-acetoxy-Anthracene  (Di-acetyl  derivative  of 
9  : 10-di-hydroxy-anthracene). 

C.O.CO.CHg 
C6H4/|\c6H4  C18H1404.  294. 

C.O.CO.CH3. 

10  gms.  (1  mol.)  of  anthraquinone  are  refluxed  for  30  minutes  with 
150  gms.  (excess)  of  acetic  anhydride,  10  gms.  of  fused  sodium  acetate  (see 
p.  506),  and  40  gms.  (excess)  of  zinc  dust,  and  the  cooled  mixture  filtered 
at  the  pump.  The  residue  is  recrystallised  three  times  from  glacial  acetic 
acid. 

C6H4(CO.)2C6H4  +  (CH3CO)20  +  H2  =  (C6H4)(CO.COCH3)2C6H4  +  H20. 

Yield. — Almost  theoretical  (14  gms.).  Colourless  needles  ;  insoluble 
in  water  ;  M.P.  260°.    (B.,  21,  1172.) 

Reaction  CVI.  Action  of  Acyl  Chlorides  on  Alcohols.  (B.,  17,  2545  ; 
19,  3218  ;  21,  2744  ;  23,  2962  ;  A.,  245,  140  ;  301,  102  ;  327,  105  ;  J.  pr., 
[2],  20,  263.) — Acid  chlorides,  especially  of  the  aliphatic  series,  react  with 
alcohols  and  phenols  to  give  esters. 

K^OH  +  K^CO.Cl  =  Kn.CO.OKj  +  HC1. 

With  aromatic  acyl  chlorides  the  reaction  is  not  so  rapid,  but  it  can  be 
greatly  facilitated  by  the  presence  of  caustic  soda  or  caustic  potash  in 
dilute  aqueous  solution  (Schotten-Baumann). 

RiOH.  +  RuCOCl  +  NaOH  =  Rn.CO.ORj  +  NaCl  +  H20. 

Other  alkalis  can  be  employed — carbonates  of  the  alkali  and  alkaline 
earth  metals — pyridine,  too,  gives  very  good  results,  though  with  poly- 
hydric  alcohols  the  number  of  groups  esterified  may  differ  with  organic 
and  inorganic  bases.  Acetyl  and  such-  like  aliphatic  derivatives  of 
hydroxy  compounds  cannot  be  prepared  in  this  way,  owing  to  the  great 
instability  of  the  acyl  chlorides  in  presence  of  alkali ;  however,  the 
esteriflcation  here  takes  place  sufficiently  rapidly  without  its  use. 

The  Schotten-Baumann  reaction  can  also  be  applied  to  primary  and 
secondary  aromatic  amines  (see  p.  296) ;  it  is  much  used  in  the  identi- 
fication of  compounds  to  which  it  can  be  applied,  by  the  preparation  of 
their  benzoyl,  phenyl  acetyl,  or  benzene  sulphonyl  derivatives. 


254  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  205.— Ethyl  Acetate  (Ethyl  ester  of  ethan  acid). 

CH3.COO.C2H5.       C4H802.  88. 

To  10  gms.  (excess)  of  absolute  alcohol,  15  gms.  (1  mol.)  of  acetyl  chloride 
see  p.  324)  are  added  drop  by  drop  with  good  cooling  and  shaking,  the 
temperature  not  being  allowed  to  rise  above  20°.  The  whole  is  carefully 
diluted  with  an  equal  volume  of  saturated  brine,  and  the  ethyl  acetate 
which  floats  on  the  surface  separated,  well  washed  with  a  50%  solution  of 
calcium  chloride  to  remove  alcohol,  dried  for  24  hours  over  calcium 
chloride,  and  fractionated,  the  fraction  74° — 81°  being  redistilled. 

CH3COCI  +  C2H5OH  =  CH3.COOC2H5  +  HC1. 

Yield. — Almost  theoretical  (16  gms.)  (see  p.  249). 
Preparation  206. — Methyl  Benzoate  (Methyl  ester  of  benzene-mono- 
carboxylic  acid). 

C6H5.COOCH3.       C8H802.  136. 

10  gms.  (1  mol.)  of  benzoyl  chloride  are  refluxed  for  15  minutes  with 
15  gms.  (excess)  of  methyl  alcohol,  and  the  product  twice  fractionated 
between  190°  and  203°. 

C6H5C0C1  +  CH3OH  =  C6H5COOCH3  +  HC1. 

Yield. — Almost  theoretical  (9  gms.).  Colourless  sweet-smelling  oil ; 
insoluble  in  water  ;  B.P.  700  199°  ;  D.  w  1-086. 

Ethyl  benzoate  (see  p.  250)  can  be  prepared  in  an  exactly  similar 
manner. 

The  following  preparation  shows  the  use  of  a  sulphonic  acid  chloride. 
Preparation  207. — Di-methyl  Sulphate  (Di-methyl  ester  of  sulphuric 
acid). 

(CH3)2S04.       C2H604S.  126. 

(Di-methyl  sulphate  is  very  poisonous,  and  great  care  must  be  taken  not  to 
inhale  any  of  its  vapour.  This  preparation  must  be  carried  out  in  a  good 
fume  cupboard.) 

100  gms.  (excess)  of  chlorosulphonic  acid  (see  p.  507)  are  placed  in  a 
250-c.c.  distilling  flask  fitted  with  a  rubber  stopper,  carrying  a  thermometer 
the  bulb  of  which  is  immersed  in  the  acid,  and  cooled  to  —10°  ;  30  gms. 
(excess)  of  pure  anhydrous  methyl  alcohol  are  slowly  dropped  in  during 
2  hours  by  means  of  a  dropping  funnel,  the  stem  of  which  is  drawn  out  to 
a  fine  point,  and  then  bent  upwards  so  that  the  opening  is  just  below  the 
surface  of  the  acid  in  the  flask.  Care  must  be  taken  that  initially  the 
stem  of  the  funnel  is  full  of  alcohol.  The  side  tube  of  the  flask  is  con- 
nected with  three  wash-bottles,  the  first  containing  cone,  sulphuric  acid, 
and  the  third  cold  water  to  absorb  the  hydrogen  chloride  evolved  ;  the 
second  is  empty,  and  reversed  to  prevent  the  water  sucking  back  into 
the  sulphuric  acid.  During  the  addition,  the  flask  is  frequently  shaken, 
and  throughout  the  temperature  must  not  be  allowed  to  rise  above  —  10°. 
When  all  the  alcohol  has  been  added,  the  mixture  is  cautiously  distilled  at 
20mms.  from  an  oil  bath  at  140°.    The  ester  which  comes  over  is  washed 


OXYGEN  TO  CARBON 


255 


with  a  little  ice-water,  dried  over  anhydrous  sodium  sulphate  for  24 
hours,  and  re-distilled  at  20  mms.  as  before. 

Cl.S02.OH  +  2CH3.OH  =  S02(OCH3)2  +  HC1  +  H20. 

Yield. — 90%  theoretical  (50  gms.).  Colourless  odourless  liquid  ;  emits 
a  very  poisonous  vapour  ;  B.P. 7i;"  188°.    (A.,  327,  105.) 

An  acid  chloride  as  prepared  from  the  acid  can  often  be  used  directly, 
without  any  special  purification. 

Preparation  208.— Dimethyl  Terephthalate  (Di-methyl  ester  of  1 :  4- 
benzene-dicarboxylic  acid). 

COOCH3. 

/\ 

C10H10O4.  194. 

coocHg. 

10  gms.  (1  mol.)  of  terephthalic  acid  (see  p.  239)  are  warmed  with 
13  gms.  (2  mols.)  of  phosphorus  pentachloride  until  liquefaction  occurs, 
20  gms.  (excess)  of  methyl  alcohol  are  added,  and  the  whole  refluxed  for 
2  hours.  On  cooling,  the  precipitate  is  filtered  off  and  recrystallised  from 
methyl  alcohol. 

PC15  CH3OH 
C6H4(COOH)2  C6H4(C0C1)2  >  C6H4(COOCH3)2. 

Yield. — 80%  theoretical  (9  gms.).  Colourless  crystals  ;  insoluble  in 
water  ;  M.P.  140°.  (A.,  245,  140  ;  J.  pr.,  [21,  20,  263  ;  D.K.P.,  38973  ; 
70483;  71446.) 

Sodium  terephthalate  can  be  used  alone  in  place  of  the  free  acid. 
The  following  preparations  exemplify  the  Schotten-Baumann  reaction. 
Preparation  209. — Methyl  Benzoate  (Methyl  ester  o£  benzene  mono- 
carboxylic  acid). 

C6H5COOCH3.       C8H802.  136. 

20  gms.  (excess)  of  methyl  alcohol  are  added  to  15  gms.  (1  mol.)  of 
benzoyl  chloride  and  then  10%  caustic  soda  solution,  until  the  whole  is 
alkaline.  The  mixture  is  well  shaken,  warmed  gently,  until  the  smell  of 
benzoyl  chloride  has  completely  disappeared,  and  poured  into  water. 
The  layer  of  ester  is  dissolved  in  ether,  the  solution  dried  over  calcium 
chloride,  and  distilled,  the  fraction  195° — 205°  being  redistilled. 

C6H5.C0C1  +  CH3OH  +  NaOH  =  C6H5COOCH3  +  NaCl  +  H20. 

Yield.— 90%  theoretical  (12  gms.)  (see  p.  254).  (B.,  17,  2545  ;  19, 
3218  ;  21,  2744  ;  23,  2962.) 

Ethyl  benzoate,  glyceryl  tri -benzoate,  etc.,  are  prepared  in  an  exactly 
similar  manner.  The  reaction  can  also  be  applied  to  phenols  and  naphthols. 

Preparation  210. — Phenyl  Benzoate  (Phenyl  ester  of  benzene -m duo- 
carboxylic  acid). 

C6H5COOC6H5.       C13H10O2.  198. 
10  gms.  (excess)  of  phenol  are  dissolved  in  100  c.cs.  of  water  and  10  gms. 


256  SYSTEMATIC  ORGANIC  CHEMISTRY 


(1  mol.)  of  benzoyl  chloride  added,  and  then  10%  aqueous  caustic  soda 
solution  until  the  whole  is  alkaline.  The  mixture  is  warmed  and  shaken 
until  the  smell  of  benzoyl  chloride  has  disappeared  ;  the  ester  which 
separates  is  filtered  off  at  the  pump,  washed  with  cold  water,  dried  on  a 
porous  plate,  and  recrystallised  from  alcohol. 

C6H5.C0.C1  +  C6H5OH  +  NaOH  =  C6H5COOC6H5  +  NaCl  +  H20. 

Yield. — Almost  theoretical  (21  gms.).  Colourless  crystals  ;  insoluble 
in  water  ;  M.P.  68°.    (B.,  17,  2545  ;  19,  3218  ;  21,  2744  ;  23,  2962.) 

a-  and  /3-naphthyl  benzoates  (M.P.  ;  56°  and  107°  respectively)  are 
similarly  prepared.    Pyridine  is  the  base  used  in  the  next  preparation. 

Preparation  211. — Mannitol  Di-benzoate  (Dibenzoic  ester  of  hexcl- 
hexan). 

C6H8(OH)4(O.OC.C6H5)2.       C20H22O8.  390. 

To  10  gms.  (1  mol.)  of  manitol  dissolved  in  500  c.cs.  of  pyridine,  50  gms. 
(excess)  of  benzoyl  chloride  are  slowly  added  in  the  warm,  the  whole 
allowed  to  stand  overnight  and  poured  into  1  litre  of  cold  10%  sulphuric 
acid.  The  ester  is  filtered  off  at  the  pump,  washed  with  cold  water  and 
recrystallised  from  alcohol. 

CH2OH  C  H  N  CH2O.OC.C6H5 

(CHOH)4  +  2C6H5C0C1— 5.  5    >  (CHOH)4  +  2HC1. 

CH2OH  CH2O.OC.C6H5 

Yield. — 80%  theoretical  (17  gms.).  Colourless  needles  ;  insoluble  in 
water  ;  M.P.  178°.    (A.,  301,  102.) 

Ethyl  acetate  can  be  prepared  in  a  like  manner. 

Reaction  CVII.   Action  of  an  Alkyl  Iodide  on  the  Silver  Salt  of  an  Acid. 

(J.  C.  S.,  67,  600.) — This  method  is  used  when  an  ester  is  not  easily  ob- 
tained by  the  usual  methods  owing  to  steric  hindrance  or  some  such  cause. 
The  silver  salt  and  alkyl  iodide  are  heated  or  shaken  together  with  or 
without  an  inert  solvent,  benzene,  etc.  The  precipitated  silver  halide  is 
filtered  off,  and  the  ester  separated  from  the  nitrate  by  distillation  or  some 
similar  method. 

RXI  +  KCOOAg  =  E.COO.Rj  +  Agl. 

Preparation  212. — Methyl  Trinitrobenzoate  (Methyl  ester  of  s-tri-nitrc- 
benzoic  acid) 

COOCH3 

o2n/Nno2 

I  C8H508N3.  271. 

XN02 

10  gms.  (1  mol.)  of  s-trinitrobenzoic  acid  are  treated  with  14  gme. 
(1  mol.  NH4OH)  of  10%  (D.  0-959)  ammonium  hydroxide  solution, 
slight  excess  of  aqueous  silver  nitrate  solution  added,  and  the  pre- 
cipitate filtered  at  the  pump,  washed  with  cold  water  and  dried  as 
described  on  p.  473.    The  dried  silver  salt  and  20  gms.  (excess)  of  methyl 


OXYGEN  TO  CARBON 


257 


iodide  are  refluxed  on  a  water  bath  for  1  hour,  excess  of  methyl  iodide  is 
distilled  off,  and  the  residue  extracted  with  boiling  alcohol  and  filtered 
The  filtrate  is  concentrated  to  small  bulk,  cooled,  and  the  precipitate 
recrystallised  from  alcohol. 

C6H2(N02)3(COOAg)[2  :  4  :  6  :  1]  +  CH3I  = 
C6H2(N02)3(COOCH3)[2  :  4  :  6  :  1]  +  Agl. 

Yield. — 80%  theoretical  (8  gms.).  Colourless  crystals  ;  insoluble  in 
water  ;  M.P.  157°.    (J.  C.  S.,  67,  600.) 

Reaction  CVIII.  Polymerisation  of  an  Aldehyde  to  an  Ester.  (B.,  20, 
647.) — In  the  presence  of  sodium  benzylate  2  mols.  of  benzaldehyde 
polymerise  to  yield  benzyl  benzoate.  The  reaction  is  peculiar  to  aromatic 
aldehydes. 

0  :  CHC6H5  /OCH2C6H5 
C6H5.CH2.ONa  +  ->    C6H5.C— 0  .  Na 

0  :  CHC6H5  \:OCn2C6H5 

C6H5CH2.O.COC6H5  +  NaOCH2C6H5. 

The  reaction  should  be  compared  with  the  simultaneous  oxidation  and 
reduction  of  aromatic  aldehydes  under  the  influence  of  concentrated 
caustic  alkali  (Reaction  LXIIL). 

Prepaeation  213. — Benzyl  Benzoate  (Phenyl-methanol  ester  of  phenyl- 
methan  acid). 

C6H5CO.O.CH2C6H5.       C14H1202.  212. 

A  solution  of  0-75  gm.  of  sodium  in  a  sufficient  quantity  of  benzyl 
alcohol  (previously  dried  over  potassium  hydroxide  and  redistilled)  is 
heated  on  a  water  bath  using  a  calcium  chloride  tube  on  the  flask,  and 
added  to  75  gms.  (2  mols.)  of  benzaldehyde  (previously  dried  over  calcium 
chloride  and  distilled  in  a  current  of  carbon  dioxide).  The  whole  is  heated 
on  a  water  bath  for  20  hours,  and  acidified  with  5  c.cs.  of  glacial  acetic 
acid.  Water  is  added,  and  the  oil  which  separates  dried  over  calcium 
chloride  and  distilled  in  a  high-temperature  distilling  flask  (see  p.  18). 
Some  unchanged  benzaldehyde  comes  over  ;  the  fraction  320°— 326°  is 
retained. 

C6H5CH2ONa 
2C6H5.CHO  >C6H5.CH2.O.CO.C6H5. 

Yield. — 80%  theoretical  (60  gms.).  Colourless  crystals  ;  insoluble  in 
water  ;  M.P.  20°  ;  B.P.  323°.    (B.,  20,  649.) 

Reaction  CIX.  Action  of  Heat  on  certain  Dibasic  Acids.  (B.,  10,  326.) 
— When  acids  such  as  phthalic  acid  or  succinic  acid,  which  contain  two 
carboxyl  groups  attached  to  adjacent  carbons,  are  heated,  they  readily 
lose  water  and  pass  into  the  acid  anhydride. 

CH2COOH  CH2CO 

CH2COOH  CH2CO 

Dibasic  acids  with  the  carboxyl  groups  not  attached  to  adjacent  carbons 
only  form  anhydrides  with  difficulty  or  not  at  all. 

S.O.C,  a 


258 


SYSTEMATIC  OKGANIC  CHEMISTRY 


Preparation  214. — Phthalic  Anhydride  (Anhydride  of  1 : 2  -benzene- 
dicarboxylic  acid). 

>0        C8H403.  148. 
,CO. 


20  gms.  (1  mol.)  of  phthalic  acid  are  sublimed  over  a  naked  flame  in  the 
apparatus  described  on  p.  28.  Long  needles  collect  on  the  filter  paper 
and  funnel. 

C6H4(COOH)2[l  :  2]         C6H4(CO)20[l  :  2], 

Yield. — Almost  theoretical  (18  gms.).  Colourless  needles ;  yield 
phthalic  acid  on  treatment  with  water  ;  M.P.  128°  ;  B.P.  284°.  (B.,  10, 
326.) 

*  Succinic  anhydride  (see  Preparation  217)  can  be  similarly  prepared. 

The  following  reactions,  unlike  the  above,  deal  mostly  with  the  prepara- 
tion of  anhydrides  in  which  the  carboxyl  groups  belong  to  different 
molecules : — 

Reaction  CX.   Action  of  an  Acyl  Chloride  on  the  Sodium  Salt  of  an  Acid. 

(A.  Ch.,  [3],  37,  311.) — This  is  a  standard  method  of  preparing  acid 
anhydrides.  By  using  the  sodium  salt  of  an  acid  different  from  the  acid 
the  chloride  of  which  is  being  taken,  mixed  anhydrides  may  be  obtained. 

KiCOONa  +  Cl.CO.Ri!  -  RiCO.O.COEn  +  NaCl. 

Simple  anhydrides  can  also  be  prepared  by  the  action  of  the  alkali  salt 
of  an  acid  on  half  the  quantity  of  phosphorus  oxy chloride  necessary  for  its 
conversion  to  the  acid  chloride  which  is  intermediately  formed. 

2CH3COONa  +  P0C13  =  2CH3C0C1  +  NaP03  +  NaCl. 
2CH3COONa  +  2CH3C0.C1  -  2(CH3CO)20  +  2NaCl. 

This  latter  method  is  used  industrially. 

Preparation  215. — Acetic  Anhydride  (Di-ethanoyl  oxide). 

(CH3CO)20.       C4H603.  102. 

10  gms.  (excess)  of  crystallised  sodium  acetate  are  heated  on  a  metal 
tray  or  in  a  porcelain  basin  until  the  crystals  melt  in  their  own  water  of 
crystallisation  (3  mols.),  solidify,  and  finally  remelt.  (Caution!)  When 
the  whole  mass  has  fused  (315°),  it  is  allowed  to  cool  and  is  powdered ; 
overheating  must  be  avoided.  It  is  immediately  introduced  into  a  250-c.c. 
retort  connected  by  a  water  condenser  to  a  receiver  consisting  of  a  distilling 
flask,  the  side  tube  of  which  is  fitted  with  a  calcium  chloride  tube  con- 
nected with  a  draught  pipe.  The  whole  apparatus  is  fitted  up  in  a  fume 
cupboard.  40  gms.  (1  mol.)  of  acetyl  chloride  are  slowly  added  by  means 
of  a  dropping  funnel  fixed  in  the  tubulus  of  the  retort,  which  is  meantime 
cooled  in  water  and  shaken  at  intervals.  When  addition  is  complete,  the 
dropping  funnel  is  removed,  the  mixture  stirred  with  a  glass  rod,  and  the 
tubulus  closed  with  a  glass  stopper.    The  retort  is  now  heated  with  a 


OXYGEN  TO  CARBON 


259 


luminous  flame,  which  is  constantly  moved  about,  until  nothing  further 
distils.  Some  fused  sodium  acetate  is  added  to  the  distillate  and  the 
latter  redistilled  from  the  receiving  flask  into  another  distilling  flask  fitted 
with  a  calcium  chloride  tube  as  before.  Each  time  before  beginning  dis- 
tillation the  air  in  the  apparatus  should  be  displaced  by  dry  air  blown  into 
it  via  the  calcium  chloride  tube  by  means  of  a  rubber  bulb  attachment. 
This  will  help  in  the  production  of  a  colourless  liquid.  In  the  second 
distillation  the  fraction  distilling  at  130° — 140°  is  collected  separately. 


Yield. — 80%  theoretical  (45  gms.).  Colourless  liquid  ;  suffocating 
smell  ;  B.P.  138°  ;  D.1*  1-08.    (A.  Ch.,  [3],  37,  311.) 

Note. — If  an  absolutely  pure  product  is  desired,  distillation  over  fused 
sodium  acetate  must  be  repeated  until  a  drop  of  the  distillate  shaken  with 
a  little  warm  water  (Caution  !)  gives  no  precipitate  on  addition  of  dilute 
nitric  acid  and  silver  nitrate.  This  test  shows  the  complete  absence  of 
acetyl  chloride. 

Propionic  anhydride,  benzoic  anhydride  (see  p.  260),  etc.,  are  obtained 
in  a  similar  manner. 

Reaction  CXI.  Action  of  Dehydrating  Agents  on  a  Free  Acid.  (B.,  34, 
186,  2074  ;  A.,  226,  8.) — This  is  a  usual  method  of  preparing  the  anhy- 
drides of  acids,  the  chlorides  of  which  are  not  readily  available.  Acetic 
anhydride  is  very  frequently  used — acetyl  chloride  can  also  be  employed. 

2K.COOH  +  (CH3CO)20  =  (RCO)20  +  2CH3COOH. 

Preparation  216. — Cinnamic  Anhydride  (Anhydride  of  3-phenyl-2- 
propen  acid). 

(C6H5CH  :  CHCO)20.       C18H1403.  278. 

50  gms.  (2  mols.)  of  dry  finely  powdered  cinnamic  acid  and  250  gms. 
(excess)  of  acetic  anhydride  are  refluxed  together  for  8  hours,  and  dis- 
tilled to  146°.  The  cold  residue  is  extracted  with  ether,  the  extract 
filtered,  and  ether  removed  on  a  water  bath.  The  residue  is  recrystallised 
from  alcohol. 


Yield. — Almost  theoretical  (46  gms.).    Colourless  needles  ;  soluble  in 
ether  and  in  hot  alcohol ;  M.P.  136°.    (B.,  34,  186,  2074.) 
Preparation  217.— Succinic  Anhydride  (Anhydride  of  butan  diacid). 


CHgCOCl  +  NaO.CO.CH3  =  (CH3CO)20  +  NaCl. 


2C6H5CH  :  CHCOOH  2_>  (C6H5CH  :  CHCO)20. 


CH2.CO 


!  > 

CH2CO. 


O. 


C4H403. 


100. 


10  gms.  (1  mol.)  of  finely-powdered  succinic  acid  are  refluxed  for  3 
hours  with  20  gms,  (excess)  of  acetyl  chloride  and  allowed  to  stand  in  a 

s  2 


260  SYSTEMATIC  ORGANIC  CHEMISTRY 


soda-lime  desiccator  until  acetyl  chloride  and  acetic  acid  are  completely 
removed.    The  residue  is  recrystallised  from  absolute  alcohol. 

CH2COOH  CH2CO 
|  -  H*°    |  >0. 

CH.COOH  CH2CO 

Yield. — Almost  theoretical  (12  gms.).  Long  needles  ;  M.P.  119-6°  ; 
B.P.10  131°  ;  B.P.7,i»  261°.    (A.,  226,  8.) 

Reaction  CXII.  Action  of  certain  Bases  on  Acyl  Chlorides.  (B.,  34, 
2070  ;  J.  pr.,  [2],  50,  479.) — When  pyridine  or  quinoline  act  on  an  acid 
chloride,  and  the  addition  product  which  is  formed  treated  with  water, 
the  acid  anhydride  is  obtained  (cf.  Reaction  CIX.). 

C  H  N 

2R.CO.C1  ^  (RCO)20  +  2HC1. 

H20 

Preparation  218. — Benzoic  Anhydride  (Anhydride  of  benzene-mono- 
carboxylic  acid). 

(C6H5CO)20.       C14H10O3.  226. 

25  gms.  (2  mols.)  of  benzoyl  chloride  are  slowly  added  to  20  c.cs.  of 
pyridine  and  8  gms.  of  anhydrous  sodium  carbonate  ;  after  J  hour  the 
whole  is  poured  into  water,  the  precipitate  filtered  and  washed  with  cold 
water,  and  dried  first  on  a  porous  plate,  and  then  in  a  desiccator.  It  is 
recrystallised  from  petroleum  ether,  which  is  removed  under  reduced 
pressure. 

Colourless  needles  ;  insoluble  in  water  ;  M.P.  42°.  (J.  pr.,  [2],  50, 
479.) 


CHAPTER  XVIII 


THE  LINKING  OF  NITROGEN  TO  CARBON 

Nitro  Compounds 

Reaction  CXIII.  Action  of  Dilute  Nitric  Acid  on  some  Organic  Com- 
pounds.— Dilute  nitric  acid,  which  very  often  acts  as  an  oxidising  agent, 
can  be  used  for  introducing  the  nitro  group,  N02,  under  certain  con- 
ditions. For  example,  phenol  can  be  converted  into  nitro-phenol  by  3% 
nitric  acid,  while  4%  acid  converts  methyl-  and  ethyl-acetanilide  into  the 
corresponding  dinitro  derivatives.  The  nitro  group  can  also  be  sub- 
stituted in  the  side  chain  by  heating,  say,  toluene  with  dilute  nitric  acid 
under  pressure.  The  reaction,  however,  is  not  generally  employed,  as  it 
is  necessary  to  boil  for  some  hours.  Sodium  and  potassium  nitrates  in 
dilute  sulphuric  acid  and  solutions  of  nitric  acid  in  glacial  acetic  acid, 
ether,  acetone,  and  acetic  anhydride  are  also  used. 

Preparation  219 . — Dinitromethylaniline. 

NO,/      \nH.CH3.       CvH704N3.  197- 
 K02 

10  gms.  methyl  acetanilide*  are  dissolved  in  1  litre  of  dilute  nitric  acid 
(D.  1-029),  and  the  solution  heated  to  boiling  under  a  reflux  condenser. 
The  liquid  instantaneously  assumes  a  brown  colour,  and  after  half  an  hour's 
heating,  becomes  turbid  and  a  yellow  substance  begins  to  separate  out. 
Two  hours'  heating  is,  however,  necessary  to  complete  the  reaction.  On 
cooling,  the  substance  separates  out  in  yellow  crystals,  which  are 
recrystallised  from  aqueous  alcohol. 

C6H5N.CH3COCH3  +  2HN03  +  H20  ->  G6H3(N02)2NH.CH3  + 
CH3COOH  +  2H20. 

M.P.  175°.    (B.,  18,  1995.) 

Reaction  CXIV.  Action  of  Concentrated  Nitric  Acid  on  Aromatic  Com- 
pounds. (B.,  20,  333.) — Concentrated  nitric  acid  up  to  100%  is 
required  for  nitrating  many  compounds  which  are  not  oxidised  by  this 
treatment.  For  this  reason  it  is  not  used  in  the  aliphatic  series,  nor  with 
compounds  containing  an  easily  oxidisable  side  chain.  The  reaction  is 
represented  by  the  equation 

KH  +  HON02  ->  E.N02  +  H20. 

In  this  reaction  the  question  of  temperature  is  one  of  importance.  In 

*  Methyl  acetanilide  is  prepared  by  heatinsj  mono-methylaniline  with  acetyl  chloride, 
It  can  be  purified  by  recrystallisation  or  sublimation.    M.P.  101°— 102°.    (B.  10,  323.) 

261 


262 


SYSTEMATIC  ORGANIC  CHEMISTRY 


general  it  should  be  kept  as  low  as  possible  to  avoid  oxidation.  When 
the  temperature  is  raised  the  tendency  to  form  dinitro,  trinitro,  and  poly- 
nitro  derivatives  is  much  increased. 
Pkeparation  220.— 4-Nitro-3-hydroxy  Benzoic  Acid. 

_COOH 

HO<^       ^>N02.       C7H505N.  183. 

50  gms.  m-hydroxy  benzoic  acid  are  dissolved  in  175  c.cs.  of  hot  nitro- 
benzene. The  solution  is  cooled  to  35° — 40°,  and  17  c.cs.  fuming  nitric 
acid  dissolved  in  an  equal  amount  of  nitrobenzene  are  slowly  added 
with  stirring  during  4  hours.  The  product  is  filtered,  washed  with  carbon 
tetrachloride,  and  crystallised  from  dilute  alcohol. 

Yield.— 15%  theoretical  (10  gms.).  M.P.  227°— 228°.  (J.  C.  S.,  119, 
1428.) 

Reaction  CXV. — Action  of  a  Mixture  of  Concentrated  Nitric  Acid  and 
Concentrated  Sulphuric  Acid  (mixed  acid)  on  Aromatic  Compounds.— This 
reaction  is  the  most  important  for  nitration  and  is  represented,  as  before, 
by  the  equation — 

R.H  +  HON02^  R.N02  +  H20. 

(a)  The  theoretical  quantity  of  nitric  acid  is  added  to  a  large  excess  of 
cone,  sulphuric  acid,  and  the  mixed  acid  added  to  the  compound  to  be 
nitrated.  Or  the  compound  may  be  dissolved  in  excess  of  cone,  sulphuric 
acid,  and  the  theoretical  quantity  of  strong  nitric  acid  then  added.  The 
excess  of  sulphuric  acid  is  added  to  absorb  the  water  formed  in  the  reaction, 
and  which  would  reduce  the  concentration  of  nitric  acid  ultimately  to  a 
point  where  no  nitration  would  take  place.  The  quantity  of  sulphuric 
acid  added  must  be  such  that  its  final  concentration  after  nitration,  i.e., 
when  it  contains  the  water  formed  in  the  reaction  plus  the  water  originally 
present  in  the  nitric  acid,  must  be  above  a  certain  minimum,  depending 
on  the  compound  to  be  nitrated.  When  this  minimum  concentration  of 
sulphuric  acid  is  reached  nitration  again  stops. 

(b)  In  nitrating  bases,  the  basic  group  must  be  protected  from  oxidation. 
This  may  be  done  in  several  ways  : — 

1.  By  carrying  out  the  nitration  in  presence  of  a  large  excess  of  cone. 
H2S04.  The  amine  sulphate  is  first  formed,  and  then  nitration  takes 
place. 

2.  By  introducing  acyl  groups  previous  to  nitration, 

E.NH2  ->  R.NH.COR!  ->  R^COR^, 

where  Rx  ==  alkyl  or  aryl  group. 
After  nitration,  the  acid  group  is  split  off  by  hydrolysis. 

H20 

NOaR.NH.CORi  >N02R.NH2  +  R^OOH. 

3.  By  combining  with  benzaldehyde  to  form  a  benzylidene  derivative, 

R.NH2  +  OCH.C6H5  ->  R.N  =  CH.C6H5, 


THE  LINKING  OF  NITROGEN  TO  CARBON 


263 


which  can  be  readily  nitrated,  and  the  benzylidene  group  removed  subse- 
quently by  hydrolysis. 

By  these  methods  usually  only  one  isomer  is  formed  in  nitration,  e.g., 

NH2 

HNO. 


NH2  NH2 

NH2 

/\t\to 

||+  H 
\/  \>°* 

u 

N02 

50%  10% 

40% 

NH.COCHg 

/\ 

NH, 

/V 

NaOH 

|      |   +'  a  little  ortho 

\/ 
N02 

\/ 
N02 

HNO, 


(vxr>  HN03  i/YYH'  + 

 > 


NO, 


H2 


/\/\nh.coch, 


HNO 


N02 

/\/\nh.coch. 


NaOH 


NO. 


H, 


(c)  Sometimes  it  is  necessary  to  protect  the  OH  group,  and  the  same 
acyl  groups  are  introduced. 

Rules  of  Nitration. — The  position  taken  by  the  N02  group  on  entering 
the  nucleus  depends  on  the  group  or  groups  already  present  in  the  nucleus. 

When  the  substance  contains  an  OH,  NH2,  CI  or  CH3  group,  nitration 
gives  a  mixture  of  ortho-  and  para-nitro  compounds.  When  a  S03H, 
COOH,  CN,  CHO,  or  N02  group  is  present,  nitration  gives  chiefly  the 
meta  compound. 

By  nitrating  toluene  by  the  usual  method,  i.e.,  using  mixed  acid,  the 
following  proportions  are  obtained  : — 

63%  ortho-,  35%  para-,  2%  meta-nitro  toluene. 

Influence  of  Temperature. — The  proportion  of  different  isomers  formed 
in  nitration  is  influenced  by  temperature.  The  table  shows  the  alteration 
in  proportion  when  nitration  is  carried  out  at  different  temperatures  on 
toluene. 


Temp. 

-  30° 
0° 
30° 


Ortho. 

55-  6% 
56% 

56-  9% 


Meta. 

2-  7% 

3-  1% 
3-2% 


Para. 

41-7% 
40-9% 
39-9% 


Analysis  of  a  Mixed  Acid. — 1.  Total  Acidity  (calculated  as  H2S04). — 
About  5  c.cs.  of  mixed  acid  are  put  into  a  tared  weighing  bottle  and  its 


264 


SYSTEMATIC  ORGANIC  CHEMISTRY 


weight  found.  This  is  then  washed  into  a  beaker  and  titrated  with 
N/caustic  soda  solution,  using  methyl  orange  as  indicator. 

°/  H  SO  —  4,9  x  ccs-  of  NaOH 
/°     2     *  —      weight  taken 

2.  Real  H2S04. — About  5  c.cs.  are  weighed  out  into  a  tared  dish,  and 
heated  on  a  water  bath  till  all  the  HN03  and  HC1  (if  any)  is  driven  off. 
This  is  then  washed  into  a  flask  and  titrated,  as  in  1. 

Total  acidity  as  H2S04  -  (hN03  x  ||)  =  real  H2S04. 
It  is  better,  however,  to  estimate  HN03  as  in  3. 

3.  HNO3  by  Nitrometer. — About  5  gms.  of  mixed  acid  are  weighed  out 
and  placed  in  the  funnel  of  a  nitrometer,  and  washed  in  with  a  little  pure 
cone.  H2S04.  The  nitrometer  is  then  shaken  until  all  the  NO  is  evolved. 
It  is  then  allowed  to  stand  till  room  temperature  is  reached,  when  the 
temperature  and  barometric  pressure  are  noted. 

The  volume  of  NO  at  N.T.P.  is  then  calculated. 
63 

This  volume  X  ^2^00  =  we^^  °^  HN02  =  x. 

%  HNO3  =      .  ,  x..  . —  X  100. 
/u         *     weight  taken 

This  figure  includes  HN02,  as  it  also  gives  NO  in  the  nitrometer.  It 
can  be  estimated  as  in  4. 

4.  HN02  (Small  Amounts). — 5  c.cs.  N/10  permanganate  solution  are 
diluted  with  distilled  water  to  100  c.cs.  The  mixed  acid  is  then  run 
in  from  a  burette  until  the  KMnO^  is  decolorised.  The  weight  of 
mixed  acid  is  then  calculated  from  its  specific  gravity. 

HNO3  by  nitrometer  -  (hN02  x  ~)  =  real  HN03 
1  mol.  KMn04  =  5  mols.  HN02. 

The  Isolation  of  Nitro  Compounds. — There  is  usually  little  difficulty 
experienced  in  isolating  liquid  nitro  compounds,  owing  to  the  differences 
in  specific  gravity  of  these  compounds  and  that  of  the  mixed  acid.  Emul- 
sions are  sometimes  formed,  but  on  standing  these  usually  separate  so 
far  as  to  give  a  partial  separation.  By  cautiously  diluting  the  mixture 
until  the  specific  gravity  of  the  nitro  compound  is  greater  than  that  of 
the  acid,  separation  may  be  effected,  and  is  usually  hastened  by  gently 
heating.  Solid  nitro  compounds  can  be  separated  by  crystallisation,  and 
in  some  cases  by  diluting  the  mixed  acid,  or  simply  pouring  into  water. 
If  both  these  methods  prove  unsuccessful,  extraction  with  ether,  after 
dilution,  may  be  attempted. 


THE  LINKING  OF  NITROGEN  TO  CARBON  265 


Preparation  221. — Nitrobenzene. 

C6H5.N02.  123. 

100  gms.  of  benzene  are  placed  in  a  vessel,  which  is  provided  with  a 
good  efficient  mechanical  agitator.  A  mixed  acid  is  made  by  taking 
140  gms.  nitric  acid  (D.  141)  and  180  gms.  cone,  sulphuric  acid,  and 
mixing  well  together.  Considerable  heat  is  generated  in  mixing  these 
acids,  and  before  proceeding  further  the  mixture  should  be  cooled. 
The  benzene  should  now  be  agitated  briskly,  and  the  mixed  acid  run 
in  slowly.  The  temperature  rises  quickly  to  about  45°  C,  when  the 
flow  of  acid  is  reduced,  and,  if  necessary,  cooling  water  applied  to  the 
outside  of  the  nitrating  vessel.  The  acid  should  now  be  added  at  such  a 
speed  that,  when  it  is  all  in,  the  temperature  has  risen  to  60°  C.  The 
temperature  is  kept  at  60° — 70°  C.  until  nitration  is  complete.  This  may 
be  tested  by  taking  a  small  sample  of  the  oil  and  pouring  into  water. 
Nitrobenzene  sinks  at  once  to  the  bottom  (D.1!  1-2116),  while  any 
unchanged  benzene  floats  on  the  surface  of  the  water  (D.  ^  0-839).  It  may 
also  be  tested  by  taking  the  specific  gravity  of  the  oil  by  means  of  a 
hydrometer.  When  nitration  is  complete,  agitation  is  stopped,  and  the 
nitrobenzene  and  the  waste  acid  run  into  a  separator,  where  it  is  allowed 
to  settle.  The  waste  acid  is  run  off  from  the  bottom  ;  water  and  a  little 
carbonate  solution  is  added,  and  the  nitrobenzene  washed. 

After  settling,  the  nitrobenzene  is  run  off  from  the  bottom,  and  freed 
from  water  by  anhydrous  calcium  chloride  until  it  is  clear.  The  water 
and  any  unchanged  benzene  may  also  be  removed  by  distillation  under 
vacuum.  The  nitrobenzene  is  then  distilled,  distillation  being  stopped 
when  the  contents  of  the  flask  turn  dark  in  colour,  the  fraction  208°  — 
212°  being  collected. 

C6H6  +  HN03->C6H5N02  +  H20. 

Yield. — 85%  theoretical  (134  gms.).  Pale  yellow  liquid  with 
characteristic  smell;  M.P.  5-7°;  B.P.  210°;  D. !?  1-2116;  important 
intermediate  for  dyestuffs.    (A.,  12,  305  ;  J.  pr.,  19,  375.) 

Preparation  222 . — m-Dinitrobenzene, 

C6H4(N02)2.  168. 

To  a  mixture  of  30  gms.  cone,  sulphuric  acid  and  18  gms.  of  fuming 
nitric  acid,  contained  in  a  flask  of  about  700  c.cs.  capacity,  12  gms.  of 
nitrobenzene  are  gradually  added  with  shaking.  The  flask  is  heated  on 
a  water  bath  in  a  fume  cupboard  until  a  test  sample  solidifies  on  pouring 
into  cold  water  ;  about  30  minutes'  heating  is  generally  required.  The 
contents  of  the  flask  are  then  poured  in  a  thin  stream  into  a  large  volume 
of  vigorously  agitated  ice-cold  water.  The  crude  dinitrobenzene,  which 
contains  about  3%  ^-dinitro-  and  1%  o-dinitrobenzene  is  filtered  off, 
washed  well  with  water,  and  recrystallised  from  alcohol. 

C6H5N02  +  HN03-^C6H4(N02)2  +  H20. 

Yield. — 75—87%  theoretical  (12 — 14  gms.).  Pale  yellow  needles  ; 
M.P.  90°.    (A.,  57,  214.) 


266  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  223.— o-  and  ^-Nitrc -Toluene  (l-Methyl-2-nitro-benzene 
(l-methyl-4-nitro-benzene)). 

NQ2 

CH3<^  ^>  and  CH3  <^  /N02       C7H702N.  137. 

100  gms.  toluene  are  placed  in  a  nitrating  vessel.  A  mixed  acid,  con- 
sisting of  150  gms.  cone,  sulphuric  acid  and  100  gms.  nitric  acid  (D.  144) 
is  cooled  and  run  into  the  toluene,  which  is  vigorously  agitated.  The 
temperature  rises  up  to  20° — 30°,  and  is  maintained  at  that,  cooling  water 
being  passed  into  the  water  bath,  if  necessary.  After  all  the  acid  has  been 
added  the  temperature  is  allowed  to  rise  to  50°.  This  temperature  is 
maintained  until  the  specific  gravity  of  the  oil  (taken  by  hydrometer)  is 
1-15.  The  oil  is  then  separated  from  the  waste  acid  in  the  usual  way, 
washed  with  water  and  sodium  carbonate  solution,  and  then  dried  on  the 
water  bath. 

Any  unnitrated  toluene  can  be  removed  by  distillation.  The  o-com- 
pound  may  be  separated  from  the  ^-compound  by  fractional  distillation, 
using  a  column.  40%  of  the  mixture  is  distilled  off,  consisting  chiefly  of 
o-compound.  The  ^-compound  is  obtained  from  the  residue  bv  cooling 
atO°C. 

If  the  mixture  is  cooled  to  about  —  20°  (see  p.  10)  the  ^-compound 
crystallises  out. 

The  mixture  consists  of  about  65 — 70%  o,  and  about  30%  p,  with  a 
small  percentage  of  the  meta-compound. 

Yield. — Total — almost  theoretical  (148  gms.).  (Z.  e.,  16,  161  ;  Phil. 
Mag.,  1876,  IV.,  1,  17.) 


0. 

m. 

p. 

a  p 

M.P.     -  10°       -  4° 

16° 

514° 

B.P.  2° 

230°— 231° 

238° 

D.  1468 

1468 

1423 

Preparation  224 . — Dinitro-chlor-benzene. 

 N02 

NO,/       ^>C1.       CeH304N2Cl.  202-5. 


350  gms.  of  a  mixed  acid  containing  50%  nitric  acid  are  placed  in  a  cast- 
iron  pot  with  good  agitation.  113  gms.  of  chlor-benzene  are  then  run  in, 
the  temperature  being  kept  under  5°  by  external  cooling.  After  all  the 
mixed  acid  has  been  added  the  stirring  is  maintained  for  another  hour 
at  5° — 10°  C.  The  temperature  is  then  slowly  raised  to  50°  and  kept 
at  this  for  1  hour.  350  gms.  cone,  sulphuric  acid  are  then  dropped  in 
very  cautiously  with  good  stirring,  and  the  mixture  finally  heated  up  to 
115°  for  half  an  hour.    After  cooling,  the  product  is  poured  into  cold  water, 


THE  LINKING  OF  NITROGEN  TO  CARBON 


267 


when  it  immediately  solidifies.  The  mother  liquor  is  poured  off  and  the 
dinitro-chlor-benzene  washed  free  of  acid  by  heating  up  in  water  beyond 
its  melting  point  (51°  C.)  and  stirring.    The  water  is  then  poured  off. 

Yield. — Almost  theoretical  (630  gms.).  Yellow  crystals  ;  M.P.  51°. 
Note. — Care  should  be  exercised  that  dinitro-chlor-benzene  is  not  allowed 
to  touch  the  skin,  as  it  is  liable  to  produce  eczema  and  sores.  (B.,  27, 
2457  ;  U.S.P.,  1220078.) 

Preparation  225. — a-Nitro-Naphthalene  (1-Nitro  naphthalene). 

NO, 

C10H7O2N.  173. 

80  gms.  nitric  acid  (D.  14)  are  mixed  with  100  gms.  cone.  H2S04  and 
300  gms.  waste  acid  from  a  previous  nitration.  The  temperature  is  raised 
to  40°,  and  100  gms.  naphthalene,  which  has  been  previously  melted,  is 
run  in  gradually,  the  agitation  being  maintained.  The  temperature  is 
not  allowed  to  rise  beyond  50°  C.  until  all  the  naphthalene  has  been  added, 
when  it  is  raised  to  60°  C.  The  nitro-naphthalene  forms  a  cake  on  the 
top  of  the  nitrating  vessel  as  soon  as  agitation  is  stopped  and  cooling  is 
applied.  The  nitration  should  be  tested  every  hour  after  the  temperature 
has  reached  60°  C.  by  removing  part  of  the  cake,  which  forms  on  cooling, 
melting  and  washing  quickly  with  dilute  sodium  carbonate  solution, 
removing  the  alkali  and  drying  with  filter  paper,  and  taking  the  setting 
point,  as  described  on  p.  17.  The  temperature  is  maintained  at  60° 
until  a  setting  point  of  56° — 58°  is  obtained.  When  nitration  is  com- 
plete agitation  is  stopped,  the  nitrating  vessel  is  cooled,  and  the  cake 
which  forms  is  removed  from  the  waste  acid.  The  cake  is  then  melted 
under  water,  and  some  sodium  carbonate  solution  added  to  remove  any 
adhering  acid.  The  cake  is  then  allowed  to  solidify,  the  wash  water  is 
run  off,  and  the  nitro-naphthalene  dried  by  heating  on  a  water  bath. 
It  may  be  recrystallised  from  alcohol. 

If  any  unchanged  naphthalene  is  present,  it  may  be  removed  by  steam 
distillation. 

+  HO.N02    ->    |     (  | 

Yield.— 90— 95%  theoretical  (121—128  gms.).    Yellow  needles  ;  M.P. 
58-5°  ;  B.P.  304°.    (D.R.P.,  100417.) 
Preparation  226. — Picric  Acid. 

NQ2 

OH<^       ^>N02       C6H307.  187. 

93  gms.  phenol  are  placed  in  the  sulphonating  pot  and  heated  to  100°, 
when  300  gms.  100%  sulphuric  acid  is  added,  the  temperature  being  kept 


268 


SYSTEMATIC  ORGANIC  CHEMISTRY 


under  110°,  and  maintained  at  this  temperature  for  an  hour  until  sulphona- 
tion  is  complete  (test).  It  is  then  cooled  down  to  0°,  agitation  being 
maintained. 

220  gms.  nitric  acid  (D.  1-5)  and  220  gms.  100%  sulphuric  acid  are 
mixed  together  and  cooled.  This  is  added  drop  by  drop  to  the  sulphonic 
acid  in  the  pot.  It  is  then  allowed  to  stand  overnight  at  ordinary  tempera- 
ture, and  is  then  very  gradually  heated  up  to  30°,  and  then  up  to  45°, 
but  no  higher. 

About  50  c.cs.  of  the  nitrating  mixture  is  then  removed  from  the  pot 
and  heated  with,  stirring  in  a  large  porcelain  basin  on  a  sand  bath  to 
110° — 125°.  The  rest  of  the  mixture  is  then  removed,  and  is  poured 
gradually  into  the  preheated  portion.  When  all  has  been  added  the 
temperature  is  kept  at  110°— 120°  for  half  an  hour.  700  c.cs.  of  water  are 
then  added  at  such  a  speed  that  the  temperature  is  kept  at  120°.  The 
picric  acid  separates  out  on  cooling,  and  is  filtered  through  cotton  and 
washed  with  water. 

Yield. — 90%  theoretical  (165  gms.).  Yellow  powder  ;  explosive  ; 
solubility  in  water  at  20°,  1  in  90  ;  M.P.  122-5°.    (A.,  43.  219  ;  B.,  2,  52.) 

Preparation  227. — (1)  ^-Nitro-acetanilide. 

N02C6H4NH.CO.CH3.  180. 

(2)  p-Nitraniline. 

N02C6H4NH2.  138. 

1.  20  gms.  of  finely  ground  acetanilide  are  added  to  80  gms.  cone, 
sulphuric  acid,  which,  is  continuously  stirred.  The  solid  slowly  dissolves, 
and  the  temperature,  which  gradually  rises,  must  not  exceed  30°.  When 
all  is  dissolved  the  solution  is  cooled  in  a  freezing  mixture  to  0°,  and  a 
mixed  acid,  previously  cooled,  containing  15-5  gms.  nitric  acid  (D.  1-38), 
and  15  gms.  cone,  sulphuric  acid  gradually  added  during  the  course  of 
5  minutes,  the  temperature  not  exceeding  3°.  When  all  is  added,  the 
solution  is  allowed  to  stand  for  2  hours  or  longer,  until  a  sample  on  pouring 
into  water  and  boiling  with  caustic  soda  gives  no  odour  of  aniline.  The 
reaction  mixture  is  poured  on  to  a  mixture  of  50  gms.  of  water  and  50  gms. 
of  ice,  when  the  nitro-acetanilide  is  precipitated.  The  precipitate  is 
filtered  off  and  washed  with  water ;  it  is  then  stirred  with  100  c.cs.  of  water, 
sufficient  sodium  carbonate  to  render  the  liquid  alkaline  to  litmus  being 
added,  and  the  whole  boiled.  By  this  treatment  any  o-nitro-acetanilide 
present  is  hydrolised,  but  the  ^-compound  remains  unchanged,  and  is 
filtered  off  at  about  50°  and  washed  with  water. 

Yield. — 90%  theoretical  (23  gms.).  May  be  recrystallised  from  alcohol 
(M.P.  207°),  but  is  generally  used  in  the  crude  form  for  further  prepara- 
tions. 

2.  j>-Nitraniline. — The  product  of  the  last  preparation  is  stirred  with 
an  equal  quantity  of  water,  20  gms.  of  35%  caustic  soda  added,  and  the 
whole  boiled  for  2 — 3  hours.  At  the  end  of  this  time  the  solution  should 
still  show  a  faint  alkaline  reaction,  and  the  hydrolysis  is  complete  when  a 
sample  dissolves  to  a  clear  solution  in  hydrochloric  acid.    The  liquet" 


THE  LINKING  OF  NITROGEN  TO  CARBON 


269 


is  cooled,  the  ^-nitraniline  filtered  off  and  washed  with  a  little  cold  water. 
It  is  practically  pure,  but  may  be  recrystallised  from  water. 

C6H5NH.COCH3  +  HN03  ->  N02.C6H4.NHCOCH3  +  H20. 
N02.C6H4NH.CO.CH3  +  H20  ->  N02.C6H4.NH2  +  CH3COOH. 

Yield.— 80%  theoretical  (21  gms.).  Yellow  needles;  M.P.  147°. 
(C.  Z.,  1912,  36,  1055.) 

p-Nitraniline  (Second  Method). — 18  gms.  of  benzylidine  aniline  are  added 
to  70  gms.  of  cone,  sulphuric  acid,  the  temperature  being  kept  below  50°. 
The  product  is  cooled  to  about  5° — 10°  and  maintained  at  this  temperature 
while  a  mixture  of  11  gms.  of  nitric  acid  (D.  1-38)  and  11  gms.  of  cone, 
sulphuric  acid  is  run  in.  After  standing  for  20  minutes  the  nitration 
mixture  is  added  to  an  equal  volume  of  water,  and  the  benzaldehyde 
removed  in  a  current  of  steam.  The  residual  liquor  is  cooled,  diluted  with 
water,  and  neutralised  with  caustic  soda  ;  this  causes  complete  separation 
in  a  very  pure  form,  of  the  ^-nitraniline,  which  is  filtered  off,  washed  with 
water  and  dried. 

C6H5N  =  CH.C6H5  +  HN03  ->  N02C6H4N  =  CH.C6H5  +  H20. 
N02C6H4N  =  CH.C6H5  +  H20  ~>  N02C6H4NH2  +  C6H5CHO. 

Yield. — 90%  theoretical  (12  gms.).  (D.R.P.,72173.) 
Preparation  228. — m-Nitrotoluidine0 

NH2/       ^>CH3.       C7H802N2.  152. 
~^02 

10  gms.  ^-toluidine  are  dissolved  in  200  gms.  cone,  sulphuric  acid.  The 
solution  is  cooled  by  a  freezing  mixture  to  below  0°.  A  mixture  containing 
7-5  gms.  nitric  acid  (D.  148)  and  30  gms.  cone,  sulphuric  acid  is  allowed  to 
flow  into  the  well-stirred  solution,  the  temperature  being  maintained  at  0°. 
When  all  the  mixed  acid  has  been  added  the  mixture  is  allowed  to  stand 
for  a  short  time  and  is  then  poured  into  500  c.cs.  of  ice-cold  water,  the 
temperature  being  kept  below  25°  by  the  addition  of  more  ice  if  necessary. 
The  solution  is  now  filtered  from  impurity  and  diluted  to  3  times  its  bulk 
and  neutralised  with  solid  sodium  carbonate,  the  temperature  being  kept 
as  low  as  possible.  The  precipitate  is  then  filtered  off,  pressed  dry  and 
finally  recrystallised  from  alcohol. 

CH 8/~  _\NH2  CH3/~  )NH2 

NOT 

Yield. — 65 — 70%  theoretical  (10  gms.).  Yellow  monclinic  needles  ; 
M.P.  77-5°.    (B.,  17,  263.) 

Reaction  CXVI. — Action  of  Nascent  Nitric  Acid  on  Aromatic  Compounds 
in  presence  of  Concentrated  Sulphuric  Acid. — This  reaction  gives  nitro 
compounds  which,  in  many  cases,  are  only  obtained  with  difficulty  by  the 
action  of  mixed  acid,    Sodium  or  potassium  nitrate  is  usually  added  to  the 


270  SYSTEMATIC  ORGANIC  CHEMISTRY 


solution  of  the  compound  in  cone,  sulphuric  acid.  It  is  usually  necessary 
to  keep  the  temperature  below  ordinary  room  temperature. 

Peepaeation  229. — o-  and  ^>-Nitrophenol  (1-Hydroxy  2-  and  4-nitro- 
benzene). 

NO^   

IK)/       \  and  HO/       \n09.       CJI.CkN.  139. 


20  c.cs.  of  water  are  added  to  94  gms.  of  phenol,  and  this  mixture  is  allowed 
to  drop  into  a  solution  of  150  gms.  sodium  nitrate  in  400  c.cs.  water  and 
250  gms.  cone,  sulphuric  acid.  The  agitation  must  be  good  and  during 
the  addition  the  temperature  must  be  kept  under  20°.  The  stirring  is 
maintained  for  2  hours  after  all  has  been  added.  A  resinous  mixture  of 
nitro  bodies  is  formed  from  which  the  supernatant  liquor  is  poured  off. 
The  residue  is  then  melted  in  500  c.cs.  of  water  and  chalk  is  added  with 
stirring  until  the  mixture  is  neutral  to  litmus.  This  frees  the  nitro  bodies 
from  acid.  The  wash  liquor  is  poured  off  and  the  nitro  bodies  are  distilled 
in  steam,  using  a  wide  air  condenser.  The  ortho  compound  passes  over. 
The  residue  in  the  flask  is  allowed  to  cool  and  is  then  filtered  from  the 
mother  liquor.  The  residue  which  contains  the  para  compound  is  then 
boiled  up  with  a  litre  of  2%  hydrochloric  acid  and  filtered  through  a 
hot  filter  (see  p.  10).  The  para  compound  crystallises  from  the  hot 
solution  in  needles. 

   N02-:   

<^       ^OH    ->    <^       ^>OH   and   N02<^  ^OH. 

Yield. — Ortho,  40  gms.  ;  para,  40  gms.  ;  total  nitrophenol,  60% 
theoretical ;  ortho  M.P.  44-3°  :  B.P.,  214°  ;  para,  M.P.  114°,  decomposes 
on  boiling.    (A.,  103,  347  ;  110,  150.) 

Peepaeation  230. — m-Nitrobenzaldehyde. 

NQ2 

<^       ^>CHO.       C7H503N.  151. 

100  gms.  benzaldehyde  is  added  to  a  cooled  solution  of  85  gms.  of  sodium 
nitrate  in  200  gms.  of  cone,  sulphuric  acid.  The  temperature  is  not  allowed 
to  rise  above  30° — 35°.  The  smell  of  benzaldehyde  disappears  after  the 
nitration  is  complete.  The  separation  of  the  o-  and  ^-compounds  which 
are  formed  is  similar  to  that  used  in  the  case  of  the  toluidines.  The 
nitration  product  is  poured  into  ice  and  water,  the  m-compound  solidifies 
and  is  filtered  from  the  oily  o-compound. 

NQ2 

<^      ^>CHO  +  HN03  ->  <^  ^>CHO 

Yield. — 100  gms.  meta  compound,  25  gms.  ortho  compound;  90% 
theoretical ;  M.P.  0-  46  °,  m-  58  °,  p-  107  °.    (B.,  14,  2802.) 


THE  LINKING  OF  NITROGEN  TO  CARBON  271 


Preparation  231. — 1.5  and  1.8  Dinitro-anthraquinone. 

CO  NO,  N02  CO  N02 

and    |      |      |  C1dH«0«N,.  298. 

NO,,  CO  CO 

10  gms.  anthraquinone  are  dissolved  in  200  gms.  cone,  sulphuric  acid; 
10  gms.  sodium  nitrate  (dry)  are  added  with  agitation.  The  mixture  is 
kept  at  60° — $0°  C.  for  12  hours.  It  is  then  poured  into  water  and  the  1.5 
and  1.8  compounds,  along  with  any  unchanged  anthraquinone,  separated 
and  washed. 

The  L5  is  separated  from  the  L8  by  using  alcohol  as  a  solvent,  the  1.8 
going  into  solution. 

Yield.— Almost  theoretical;  M.P.  1.5-  above  330°;  1.8-  above  312°. 
(B.,  16,  363.) 

Preparation  2 32 . — 2.2 '-Dinitro-benzidine. 

NH2/  \-/  )NH2.       C12H10O4N4.  274. 

~^02    N02  ' 

To  56  gms.  of  pure  benzidine  sulphate  600  gms.  of  pure  cone,  sulphuric 
acid  are  added  and  the  mixture  well  stirred.  Solution  is  completed  by 
heating  up  to  60°  if  necessary.  The  solution  is  cooled  down  to  about  10°, 
but  not  lower,  and  40  gms.  potassium  nitrate  slowly  added.  After  several 
hours'  stirring  the  solution  is  poured  into  about  2  litres  of  cold  water  and 
the  dinitro-benzidine  sulphate,  which  is  precipitated,  filtered  off  and 
washed  with  a  little  water.  The  sulphate  is  then  made  into  a  cream  with 
hot  water  and  caustic  soda  solution  added  until  an  alkaline  reaction  is 
given  to  phenolphthalein.  The  free  base  is  then  filtered  off,  washed  with 
water,  and  recrystallised  from  water  or  from  alcohol. 

NH2<C  I/~\ZI)NH2  NH2\H/~\ZI>HN2 

N02  N02 

Yellow  leaflets,  M.P.  214°.    (B.,  23,  795.) 

Reaction  CXVII.  Action  of  Nitrous  Fumes  on  Certain  Organic  Com- 
pounds.—The  nitro  group,  N02,  can  be  introduced  in  some  cases  by  the 
action  of  nitrous  fumes,  the  nitrous  fumes  being  passed  through  the  solu- 
tion in  glacial  acetic  acid.  Sodium  nitrite  in  acid  solution  may  also  be 
used,  and  this  reaction  gives  good  yields  with  amines  and  phenols,  the 
amines  passing  through  the  diazo  stage  into  phenols,  e.g., 


OH  OH 

/\NO, 


(90  %  yield). 


COOH  COOH 


272 


SYSTEMATIC  ORGANIC  CHEMISTRY 


The  nitrous  acid  in  the  reaction  is  oxidised  to  nitric  acid,  and  this 
produces  nitration. 

3HN02  ->  HN03  +  2NO  +  H20. 

NH2  N  =  NHS04      OH  OH 

/X  /\  /\NO, 

j  — *  >  and 

When  the  ^-position  is  occupied,  the  yield  is  almost  theoretical,  e.g., 
CH3  CH3 


NH2  OH 
Preparation  233. — m-Nitro-Salicylic  Acid. 

OH 

/       ^COOH       C7H505N.  183. 

NOT/ 

100  gms.  salicylic  acid  and  130  gms.  sodium  nitrite  are  mixed  with  150  c.cs. 
water  and  1,200  c.cs.  sulphuric  acid  (D.  1-52)  are  slowly  added,  the  tempera- 
ture being  kept  below  15°.  After  4  hours  the  mixture  is  warmed  to  50° 
and  then  set  aside  till  the  evolution  of  nitrous  fumes  ceases.  The  mass  is 
then  warmed  on  the  water  bath.  On  cooling,  crystals  of  m-nitro  salicylic 
acid  separate  out,  and  are  filtered  off,  washed  and  recrystallised  twice  from 
water. 

-     OH  OH 

<^       ^>COOH    ->    <^  ^>COOH. 


Yield.— 64%  theoretical  (85  gms.).  Needles  ;  M.P.  228°.  (J.  pr.,  [11], 
42,  550.) 

Preparation  234. — o  and  ^-nitrophenol. 

  N02   

(       ^>OH  and  OH/       ^NO,.       CfiH,0,N.  139. 


10  gms.  aniline  are  dissolved  in  100  c.cs.  of  25%  sulphuric  acid  and  the 
solution  cooled  to  15°.  300  gms.  sodium  nitrite  are  dissolved  in  100  c.cs. 
water  and  this  solution  added  in  two  portions.  When  the  first  third  is 
added  cooling  is  applied,  and  the  remainder  of  the  nitrite  is  added  without 
cooling.  The  mixture  is  then  poured  into  a  large  evaporating  basin  on  a 
water  bath  and  boiling  50%  sulphuric  acid  is  cautiously  added.  When  the 
action  is  over,  the  whole  is  steam  distilled  when  the  o-nitro-phenol  passes 


THE  LINKING  OF  NITROGEN  TO  CARBON 


273 


over.  The  ^-compound  is  then  extracted  from  the  residue  as  in 
Preparation  229. 


^>NH2  ->  ^>N2.HS04        N02<^       ^>OH  and  <^  ^OH 

~N02 

Yield. — o-compound  (4-7  gms.),  ^-compound  (3-3  gms.),  total  53% 
theoretical  (see  p.  270).    (J.  pr.,  148,  298.) 

Reaction  CXVIII.  Action  of  Nitrous  Acid  on  Aromatic  Amines  in 
presence  of  Cuprous  Salts  (Sandmeyer). 

K.NH2  — >  R.N02. 

For  other  examples  and  a  discussion  of  the  Sandmeyer  reaction,  see 
pp.  149,  338. 
Peeparation  235. — Nitrobenzene  (Sandmeyer). 

C6H5N02.  123. 

9  gms.  aniline  are  mixed  with  50  c.cs.  water  and  20  gms.  cone,  nitric  acid 
(D.  1-4).  The  solution  is  cooled  to  below  5°  and  15  gms.  sodium  nitrite  in 
50  c.cs.  water  added.  The  mixture  is  then  poured  into  a  flask  containing 
the  cuprous  salt,  prepared  by  dissolving  50  gms.  cupric  sulphate  and  15  gms. 
grape  sugar  in  100  c.cs.  water,  and  adding  20  gms.  caustic  soda  in  60  c.cs. 
water  to  the  boiling  solution  ;  the  mixture  is  shaken  till  all  the  copper  is 
reduced,  and  is  then  rapidly  cooled,  and  finally  neutralised  by  a  slight 
excess  of  acetic  acid. 

The  combined  mixtures  are  allowed  to  stand  for  1  hour,  or  until  the 
evolution  of  nitrogen  ceases.  The  nitrobenzene  is  then  separated  by 
steam  distillation. 

<(  ^>NH2   ->    <(      ^>N2NQ3    ->    <(  ^>N02. 

Yield.— 50%  theoretical  (5  gms.).    Yellow  liquid  ;  M.P.  5-7°  ;  B.P. 
210°.    (B.,  20,  1494.) 
Reaction  CXIX.   Action  of  Silver  Nitrite  on  Alkyl  Halides. 

E.I  +  AgX02  ->  R.N02  +  Agl. 

This  is  the  only  method  of  preparing  aliphatic  nitro  compounds. 
Pkepaeation  236. — Nitro-methane  (Nitro-methan). 

CH3N02.       CH302N.  61. 

44  gms.  (slight  excess)  of  dry  silver  nitrite  (see  p.  505)  are  mixed  with 
an  equal  bulk  of  dry  sand  and  placed  in  a  reflux  apparatus  ;  41  gms. 
(1  mol.)  of  methyl  iodide  are  gradually  added,  and  the  whole  heated  on  a 
water  bath  for  2  hours.  The  mixture  is  then  distilled  from  a  water 
bath,  the  fraction  95° — 101°  being  separately  collected.  It  is  redistilled 
over  silver  nitrite  to  remove  the  last  traces  of  iodide. 

CH3I  +  AgN02  ->  Agl  +  CH3N02. 

Yield. — 70%  theoretical  (12  gms.).  Heavv,  inert,  insoluble,  colourless 
liquid  ;  B.P.  101°  ;  D.  lf  1-0236,  D.  \  M580'    (A.,  171,  18.) 

S.O.C.  T 


274  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  237. — Nitro-ethane  (Nitro-ethan). 

C2H5.N02.       C2H502N.  75. 
By-product.— Ethyl  Nitrite  (Ethyl  ester  of  nitrous  acid). 

C2H5.0.X0.       C2H502X.  75. 

42  gms.  (a  slight  excess)  of  dry  silver  nitrite  (see  p.  505)  are  placed 
in  a  round-bottomed  flask  fitted  with  a  reflux  condenser.  If  a  yield 
of  ethyl  nitrite  is  required  ice-water  must  be  used  in  the  condenser, 
which  should  be  a  long  one.  34  gms.  (1  mol.)  of  ethyl  iodide  are  added, 
gradually,  through  the  condenser  tube,  so  that  the  liquid  boils  vigorously, 
but  not  too  violently.  The  flask  must  not  be  disturbed  during  the  process 
for  it  is  important  that  the  silver  nitrite  should  be  gradually  penetrated 
by  the  iodide.  The  flask  is  then  warmed  for  2  hours  on  a  water  bath, 
well  cooled,  fitted  to  a  distillation  apparatus,  and  the  contents  fractionally 
distilled.  Ethyl  nitrite  distils  over  at  68°,  and  is  collected  in  the  same  way 
as  ether  (see  p.  208)  in  a  flask  cooled  in  a  good  freezing  mixture.  The 
temperature  then  rises  and  the  second  fraction,  nitroethane,  is  collected 
at  110°— 114°  and  redistilled. 

C2H5I  +  Ag^02        C2h5oNO  +  AgL 

Yield. — Nitro-ethane  :  50%  theoretical  (8 — 9  gms.).  Colourless  liquid  : 
insoluble  in  water  ;  B.P.  113°— 114°  ;  D.  ?  1-058. 

Yield. — Ethyl-nitrite:  50%  theoretical  (8 — 9  gms.).  Volatile  liquid  ; 
oppressive  odour  ;  resembling  that  of  apples  when  dilute  ;  B.P,  17°  ; 
D.  1545  0-947.    (A.,  171,  18.) 

Reaction  CXX.  Action  of  Concentrated  Nitric  Acid  on  Certain  Sulphonic 
Acids. 

R,S03H  +  HN03^  R.N02. 

This  reaction  goes  easily  in  the  anthraquinone  series,  but  only  in  the 
naphthalene  series  when  the  S03H  is  in  a  special  position — the  a  position. 

OH  OH 
I  +  HXO3  -> 

SO3H  N02 

In  the  process  of  nitration  with  mixed  acid,  in  many  cases  a  sulphonic 
acid  is  formed  in  the  first  instance,  the  sulphonic  group  being  ultimately 
replaced  by  the  N02  group. 

Reaction  CXXI. — Action  of  Tetranitromethane  on  Bases.  (B.,  1920,  53, 
1529.) — The  tetranitromethane  is  decomposed  by  weak  bases  in  alcohol 
or  acetone  solution  into  nitroform  and  nitric  acid 

C(N02)4  +  H20  ->  HC(X02)3  +  HNO3, 

the  base  becoming  nitrated  during  the  process. 


CHAPTER  XIX 

THE  LINKING  OF  NITROGEN  TO  CARBON  (continued) 

Reaction  CXXII.  Action  of  Phenols  and  Primary  Aromatic  Amines 
on  Diazonium  Compounds. — Diazonium  compounds  combine  with  phenols 
and  aromatic  bases  to  form  azo  dyestuffs. 

H 

E — N — CI  +  H.E1.NH2    ->  R.N.C1 

IIL  (°H)  II 

N  N.R1.NH2(OH) 

Intermediate  compound. 

HC1  is  split  off  and  an  azo  colour  is  formed. 

R — N  =  N.R1.NH2(OH). 

The  process  is  known  as  "  coupling."  R  is  seldom  aliphatic.  In  the 
azo  compound  N  is  trivalent,  while  in  the  diazonium  compound  N  is 
pentavalent.  The  diagram  shows  the  name  given  to  the  different  groups 
in  the  azo  compound. 


(OH) 

(OH) 

NH2 

NH2 

I 


N     =     N  — 


auxo chrome  group. 

chromogen  group, 
chromophore  group. 


Laws  of  Formation  of  Azo  Colours 

Bases  are  "  coupled "  in  slightly  acid  solution,  while  phenols  are 
"  coupled  "  in  shghtly  alkaline  solution. 

Coupling  usually  takes  place  in  the  ^-position  to  the  NH2  or  OH  group, 
and,  if  this  is  occupied,  in  the  o-position,  but  never  in  the  m-position. 

If  the  NH2  or  OH  groups  are  substituted  by  an  acetyl  group  no 
coupling  takes  place,  e.g. 


NH.COCH, 


O.COCH. 


or 


do  not  couple. 


If  the  NH2  is  substituted  by  an  alkyl  or  aryl  group  coupling  takes 
place,  e.g. 

NH.CH3  NH.C6H5 


and 


do  couple. 


If  the  H  in  OH  is  replaced  by  any  group,  no  coupling  takes  place. 

275  t  2 


276  SYSTEMATIC  OKGANIC  CHEMISTRY 


When  both,  an  OH  and  NH2  are  present  in  the  azo  component  (the  com- 
pound which  is  diazotised  is  termed  the  diazo  component),  and  coupling 
does  take  place,  e.g.,  H  acid,  then  the  coupling  can  be  carried  out  in  acid 
or  in  alkaline  solution,  taking  place  in  the  ortho  position  to  the  NH2  in 
acid  solution,  and  ortho  to  the  OH  in  alkaline  solution. 

When  one  azo  component  is  used  then  the  colour  is  termed  a  mono-azo 
colour. 

When  two  azo  components  are  used,  e.g.,  with  benzidine,  then  dis-azo 
colours  are  formed,  e.g. 


benzidine 


benzidine 


salicylic  acid. 


salicylic  acid, 
resorcinol. 


1 


a-naphthylamineJ  — >  N.W.  acid  (Trisazo  colour). 


The  sign  ->  being  used  to  indicate  "  coupled  to." 
For  examples,  see  section  on  Dyes,  etc. 

Reaction  CXXIIL— Action  of  Nitrous  Acid  on  Phenols,  and  Tertiary 
Aromatic  Amines.    (A.  277,  85.) 


^>OH 
>N(CH3)2 


HN02 
HNOo 


NO: 

NO< 


"V(CH3)2. 


The  nitrous  acid  is  usually  generated  by  the  action  of  sodium  nitrite 
on  the  acid  solution.  The  nitroso  phenols  are  identical  with  the  quinone 
oximes,  formed  by  acting  on  quinone  with  hydroxylamine. 


no/ 


>OH 


=  NOH 


The  NO  group  in  the  benzene  series  is  introduced  in  the  para  position 
in  both  cases.  In  the  naphthalene  series  the  ^-compound  gives  the 
1-nitroso  compound,  while  the  a-compound  gives  a  mixture  of  the  2-  and 
4-nitroso  compounds. 

NO 


OH 


OH 


OH 


+ 


OH 


THE  LINKING  OF  NITROGEN  TO  CARBON 


277 


Dihydroxy  phenols  give  di-nitroso  compounds. 

0 

OH  OH  || 

/^NO  /^^NOH 
'  or 
OH  I     JOH         I  J=0 


NO 

NOH 

Kesorcinol  Resorcin  green 

Nitrous  acid  has  no  action  with  tertiary  aliphatic  amines  and,  with 
alcohols,  yields  nitrites. 
Preparation  238. — £>-Nitroso-Phenol. 

0H<^       ^>N0.       C6H502N.  123. 

100  gms.  of  phenol  are  dissolved  in  a  solution  of  50  gms.  of  caustic  soda, 
100  gms.  sodium  nitrite  and  2  litres  water.  The  temperature  is  reduced 
to  7°.  200  c.cs.  cone,  sulphuric  acid  ar3  added  to  600  c.cs.  water,  and  when 
cooled  is  gradually  run  into  the  solution.  The  nitroso-phenol  gradually 
separates  out,  and  after  stirring  for  2  hours,  is  filtered  of!  and  washed  with 
ice  water. 

<^       ^>OH  +  HO. NO    ->    HO<^  y^O. 

Yield. — 95%  theoretical  (124  gms.).  Colourless  crystals  ;  soluble  in 
hot  water,  alcohol,  and  ether  ;  M.P.  126°  C.  with  violent  decomposition. 
(A.,  277,  85.) 

Preparation  239. — Nitroso-/?-Naphthol  (l-nitroso-2-hydroxy  naphtha- 
lene). 


NO 
\0H. 


C10H7O2N.  173. 


10  gms.  /?-naphthol  are  dissolved  in  2-8  gms.  caustic  soda  in  100  c.cs., 
water,  and  made  up  to  200  c.cs.  with  water.  5  gms.  sodium  nitrite  dis  • 
solved  in  a  little  water  are  carefully  added.  The  mixture  is  cooled  by  the 
addition  of  100  gms.  ice,  and  140  c.cs.  10%  sulphuric  acid  are  slowly  run 
in  with  constant  stirring,  the  temperature  being  kept  below  5°.  The 
nitroso  compound  separates  as  a  pale  yellow  precipitate.  It  is  allowed  to 
stand  for  2  hours,  filtered,  and  washed  with  water  until  the  washings  are 
only  slightly  acid.    It  is  then  dried  and  crystallised  from  petroleum  ether. 

NO 


Yield.— Almost  theoretical  (12  gms.).  Red  needles  ;  M.P.  110°  C. 
sparingly  soluble  in  water.    (B.,  27,  3075.) 


278  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparaton  240. — j9-Nitroso-Dimethylaniline. 

NO^      XN(CH3)2.       C8H10ON2.  150. 

10  gms.  dimethylaniline  are  dissolved  in  26  gms.  cone,  hydrochloric 
acid  in  50  c.cs.  water,  and  cooled  in  a  freezing  mixture.  6  gms.  sodium 
nitrite  in  10  c.cs.  water  are  then  slowly  added  with  constant  stirring.  The 
separation  of  the  hydrochloride  of  nitroso  di-methylaniline  soon  begins. 
After  standing  for  ^  hour  it  is  filtered  and  washed  with  about  20  c.cs. 
alcohol,  to  which  1  or  2  c.cs.  hydrochloric  acid  has  been  added.  The 
hydrochloride  is  then  made  into  a  paste  with  water  and  caustic  soda 
solution  added  in  the  cold  till  alkaline.  The  yellow  colour  of  the  salt 
changes  to  the  green  of  the  free  base.  The  base  is  now  filtered  and  the 
residue  well  pressed.    It  may  be  crystallised  from  benzene. 

(CH3)2N<^      ^>  +  HONO  ->  (CH3)2N<^      ^>NO  +  H20. 

Yield. — Almost  theoretical  (12  gms.).  Green  crystals  ;  M.P.  85°  ; 
somewhat  volatile  in  steam  ;  used  in  preparation  of  oxazine  dyestuffs. 
(B.,  7,  810  ;  8,  616  ;  12,  523.) 

Reaction  CXXXV.  Action  of  Nitrous  Acid  on  Secondary  Amines,  and 
subsequent  Rearrangement  of  the  Products. 

E2.NH   ;-  HO.NO  ->  E2N.NO. 

The  nitrosamines  are  neutral  oily  liquids  of  little  importance  in  them- 
selves. This  reaction,  however,  serves  to  separate  secondary  bases  from 
mixtures  of  primary,  secondary  and  tertiary.  The  aromatic  nitrosamines 
undergo  an  interesting  rearrangement  when  heated  with  alcoholic  hydro- 
chloric acid  (B.,  20,  1247),  the  nitroso  group  migrating  to  a  position  in 
the  nucleus,  forming  ^-nitroso  compounds. 

.NO 

C6H5N<         ->  NOC6H4NH.CH3. 

XCH3 

Preparation  241 . — ^-Nitroso-Methylaniline. 

NO<^      ^>NH.CH3.       C7H8ON2.  136. 

Methylaniline  (1  mol.)  is  dissolved  in  hydrochloric  acid  until  strongly 
acid,  and  then  treated  with  a  20%  solution  of  sodium  nitrite  (1  mol.). 
Methyl-phenyl  nitrosamine  separates  as  a  yellow  oil,  which  solidifies  on 
cooling  (M.P.  12° — 15°).  2  gms.  methyl-phenyl  nitrosamine  are  dissolved 
in  4  gms.  ether.  8  gms.  absolute  alcohol  which  have  been  saturated  with 
hydrochloric  acid  gas  are  then  added  and  after  a  time  needles  separate  out, 
which  are  filtered  and  washed  with  a  mixture  of  alcohol  and  ether. 

<^      ^>NHCH3  ->  <^      ^>N.NO.CH3  ->  NO<^  ^>NH.CH3. 

Yield.— Almost  theoretical ;  M.P.  118°.    (B.,  19,  2991.) 


THE  LINKING  OF  NITROGEN  TO  CARBON 


279 


Reaction  CXXV.  Action  of  Alkyl  Halides  on  Phthalimide  (Potassium 
Salt). — When  an  alcoholic  solution  of  phthalimide  is  treated  with  the 
theoretical  quantity  of  caustic  potash  dissolved  in  alcohol,  a  crystalline 
compound — potassium  phthalimide — separates  out  (see  p.  420). 

CO  .CO 
C6H4<       )NH  ->  C6H4<  >N.K. 
X!(K  X!<K 

When  this  salt  is  treated  with  alkyl  halide,  a  derivative  of  phthalimide 
is  formed. 

CO.  .CO 

c6h4<     >n.k  +  r.i  ->  c6h4<     >n.r  +  ki. 
xkk  xkk 

The  reaction  is  used  chiefly  with  alkyl  halides,  although  when  certain 
acidic  groups  are  present  in  the  nucleus  in  the  o-  and  ^-position  to  the 
halogen,  the  reaction  gives  satisfactory  results  with  aryl  halides. 

When  the  phthalimide  derivative  is  hydrolysed,  primary  amines  are 
formed,  so  that  the  reaction  is  useful  for  preparing  certain  aliphatic 
amines. 

yCOv  XJOOH 
C6H4<       >N.R  +  2H20  ->  C6H4<  +  R.NH2. 

X)0/  \COOH 

A  similar  reaction  can  also  be  used  for  the  preparation  of  amino  acids, 
e.g., 

/co\  /C0\ 
C6H4<       >NK  +  C1CH2C00C2H5  ->  C6H4<  >N.CH2COOC2H5 

xkk  \co/ 

H20  /COOH  H20  /COOH 

 >  C6H4<   >   C6H4<  +  NH2CH2COOH. 

(KOH)  \CONH.CH2COOH  (HC1)  ^COOH 

Reaction  CXXVI. — Action  of  Hydroxylamine  on  Aldehydes  and  Ketones. 

— The  majority  of  aldehydes  and  ketones  react  with  hydroxylamine, 
forming  oximes. 

RRxCO  +  NH2OH  ->  RRXC  =  NOH  +  H20. 

Hydroxylamine  hydrochloride  (NH2OH.HCl)  is  generally  used  ;  in 
most  cases  the  free  base  is  liberated  by  the  subsequent  addition  of  the 
theoretical  quantity  of  a  basic  substance  (caustic  potash,  sodium  car- 
bonate, etc.).  Writh  aldehydes  it  is  advisable  to  reduce  the  quantity  of 
alkali  to  a  minimum,  and  to  warm  but  gently,  if  at  all.  Ketones  react 
much  less  readily  and  usually  require  vigorous  heating  for  2 — 3  hours. 
The  reaction  is  mostly  carried  out  in  aqueous-alcoholic  solution.  The 
purification  of  some  oximes  is  best  effected  by  distillation  under  reduced 
pressure. 


280  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  242. — Acetophenone  Oxime. 

C  H 

5^C  :  NOH.        C8H9ON.  135. 
CR/ 

To  5  gms.  (1  mol.)  of  hydroxy lamine  hydrochloride,  dissolved  in  10  c.cs. 
of  water  and  contained  in  a  flask,  3  gms.  (less  than  1  mol.)  of  potassium 
hydroxide  dissolved  in  5  c.cs.  of  water  are  added.  8  gms.  (slightly  less 
than  1  mol.)  of  acetophenone  are  then  added,  and  the  mixture  heated  in  a 
reflux  apparatus  on  a  boiling  water  bath.  Alcohol,  in  small  quantities  at 
a  time,  is  added  down  the  reflux  condenser  until  the  boiling  solution  just 
becomes  clear.  After  an  hour  heating  is  stopped,  the  solution  cooled, 
and  a  drop  tested  with  litmus  paper.  It  should  be  acid  owing  to  the 
absorption  of  the  hydroxylamine  by  the  ketone.  Caustic  potash  solution 
is  carefully  added  until  the  solution  is  no  longer  acid.  The  condenser 
is  again  attached,  and  boiling  continued  for  about  30  minutes,  at  the  end 
of  which  time  the  solution  is  tested,  and  if  acid,  is  neutralised  with  caustic 
potash.  After  about  10  minutes  further  boiling  the  solution  is  once  more 
tested  with  litmus,  and  a  few  drops  of  it  mixed  with  ice  water.  If  the 
test  sample  solidifies  quickly,  the  reaction  is  complete,  and  the  contents 
of  the  flask  are  poured  into  100  c.cs.  of  water  containing  a  few  lumps  of 
ice.  (If  the  test  sample  does  not  solidify,  further  heating  is  necessary.) 
The  water  should  be  vigorously  stirred  during  the  addition  to  cause  the 
separation  of  the  oxime  in  small  lumps  and  flakes.  The  product  is  filtered 
off,  washed  with  water,  pressed  on  a  porous  plate  to  dry,  and  recrystallised 
from  petroleum  ether. 

CH3X  CH3X 

>>CO  +  H2NOH  ->  =  NOH. 

C6H5  C6H5  ^0 

Yield.— 89%  theoretical  (8  gms.).  Colourless  needles:  M.P.  m°  ; 
B.P.763246°  (with  decomposition)  ;  B.P.20  156°— 157°  (without  decom- 
position).   (B.,  15,  2781.) 

Preparation  243. — Camphoroxime  (Oxime  of  (/-camphor). 

CH, 

r  ;X  (!>!!! 

C10H17ON.  167. 


10  gms.  (excess)  of  hydroxylamine  hydrochloride,  dissolved  in  the 
minimum  amount  of  water,  are  added  to  10  gms.  (1  mol.)  of  camphor 
dissolved  in  150  gms.  of  90%  alcohol,  and  the  mixture  treated  with 
15  gms.  of  solid  caustic  soda.  The  whole  is  heated  on  a  water  bath, 
alcohol  being  added  if  necessary  to  keep  the  camphor  in  solution,  till  after 
about  an  hour's  heating  no  camphor  is  precipitated  on  diluting  a  test 
portion  of  the  liquid  with  an  excess  of  water.  The  whole  liquid  is  then 
diluted  with  a  large  excess  of  water,  filtered  if  necessary  from  a  very  small 


THE  LINKING  OF  NITROGEN  TO  CARBON  281 


precipitate  that  may  come  down,  and  slightly  acidified  with  acetic  acid. 
The  precipitated  camphoroxime  is  recrystallised  from  dilute  alcohol. 

C9H16CO  +  H2NOH  =  C9H16CNOH  +  H20. 

Yield.— 75%  theoretical  (8  gms.).  Colourless  crystals;  M.P.  115°. 
(B.,  22,  605.) 

Preparation  244. — Benz-anti-aldoxime  (a-Benzaldoxime). 

C6H5C.H 

||        C7H7ON.  121. 
HON 

14  gms.  of  caustic  soda  dissolved  in  40  c.cs.  of  water  and  21  gms.  of 
benzaldehyde  are  mixed  in  a  flask.  14  gms.  of  hydroxy lamine  hydro- 
chloride are  added  in  small  portions  at  a  time,  the  mixture  being  con- 
tinually shaken.  The  benzaldehyde  gradually  disappears,  and  some  heat 
is  developed.  On  cooling,  the  hydrochloride  of  benzaldoxime  separates. 
Sufficient  water  is  added  to  redissolve,  and  carbon  dioxide  is  passed  in 
until  saturated.  The  oxime  then  separates,  and  is  extracted  with  ether  ; 
the  ethereal  solution  is  dried  over  anhydrous  sodium  sulphate.  The 
ether  is  removed  (see  p.  32),  and  the  residue  distilled  under  greatly 
diminished  pressure. 

C6H5.CHO  +  NH2OH  ->  C6H5CH  :  NOH  +  H20. 

Yield.— 50%  theoretical  (12  gms.).  M.P.  34°;  B.P.11  123°;  B.P.10 
118°. 

Reaction  CXXVII.  Action  of  Acids,  Acid  Chlorides,  Anhydrides  and 
Phosphorus  Pentachloride  on  Oximes  (Beckmann  Transformation).  (B., 
20,  1507.) — Aldoximes  (oximes  obtained  from  aldehydes)  exist  in 
two  stereoisomeric  forms  depending  on  the  relative  position  of  the  OH 
group. 

R.C.H  R.C.H 

.11  ■  II 

N.OH  OH.N 
%/i-aldoxime.  A  nti- a  Id  oxime. 


Syh -aldoximes  give  nitriles  with  dehydrating  agents,  such  as  acety 
chloride, 

H 

R.C=N 


R.C 

II 
N 


OH 


while  <mfa-aldoximes  give  usually  acetyl  derivatives. 

R.C.H  R.C.H 

II.  — >  II 
HON  CH3CO.ON. 

When  H  is  replaced  by  R,  then  no  isomerism  occurs. 

R.C.R 

II 

NOH. 


282 


SYSTEMATIC  ORGANIC  CHEMISTRY 


If  H  is  replaced  by  R1?  as  in  the  case  of  mixed  ketones,  isomerism  again 
occurs. 

II  II 
NOH  OH.N. 

The  one  isomer  can  usually  be  transformed  into  the  other  by  heat, 
exposure  to  light,  or  treatment  with  hydrochloric  acid.  When  these 
isomers  are  treated  with  the  reagents  mentioned  (p.  281)  a  rearrangement 
takes  place  in  the  molecule,  especially  with  aromatic  aldoximes  and 
mixed  ketoximes,  due  to  the  migration  of  the  OH  group. 

RCRX  R.C.OH 

(1)  II  ->  II 
N.OH    .  RPN. 

RCRi  OH.C.Ri 

(2)  ||  ->  II 
OH.N  N.R. 

These  intermediate  compounds  are  then  immediately  transformed  into 
tautomeric  forms,  giving  acid  amides. 

(1)      R.CO.NHRi  and  (2)  R^ONH.R. 


II 

N.OH 

oxime  of  phenyl  p-tolj\  ketone.  benzo-p-toluidide. 

C6H5C.C6H4CH3 

||  ->  C6H5NH.CO.C6H4CH3. 

OH.N  anilide  of  ^-toluic  acid. 

The  configuration  of  the  oxime  can  be  determined  bv  an  examination 
of  the  transformation  product.    (Contrast  B.,  20,  1507  with  B.,  54,  3206). 

Prepakation  245. — Transformation  of  Acetophenone-oxime  (Beckmann). 

5  gms.  acetophenone-oxime  are  dissolved  in  60  c.cs.  of  ether,  which  has 
been  dried  over  metallic  sodium  and  redistilled,  and  to  this  solution  is 
gradually  added  7 — 8  gms.  of  powdered  phosphorus  pentachloride.  The 
ether  is  then  removed  by  distillation.  To  the  residue  after  cooling  is  added 
slowly  25  c.cs.  of  water.  The  acetanilide  is  then  filtered  off  and  recrystal- 
lised  from  water,  when  its  melting  point  is  taken. 

M.P. 

Acetophenoneoxime  ..  .  .  .  59° 
Acetanilide  112° 

CH3C.C6H5  CH3CO 

N.OH  NH.C6H5. 
(B.,  19,  989  ;  20,  1507.) 

Reaction  C XXVIII.  Action  of  Phenylhydrazine,  etc.,  on  Aldehydes  and 
Ketones. — Phenylhydrazones  of  aldehydes  and  ketones  are  generally 
formed  by  warming  these  substances  in  aqueous-alcoholic  solution  with 


THE  LINKING  OF  NITROGEN  TO  CARBON 


283 


phenylhydrazine,  phenylhydrazine  acetate  or  phenylhydrazine  hydro- 
chloride in  presence  of  excess  sodium  acetate.  Derivatives  of  phenyl- 
hydrazine  (e.g.,  £>-nitro-phenylhydrazine)  also  react  in  a  similar  manner. 

a-hydroxy  aldehydes  and  a-hydroxy  ketones  can  react  with  3  mols. 
of  phenylhydrazine  in  the  following  manner  : — 

— CHOH.CHO  +  H2N.NH.C6H5^  —  CHOH.CH  =  N.NH.C6H5  +  H20. 

— CH.OH.CH  =  N.NH.C6H5  +  NH2.NH.C6H5  —> 
— CO.CH  =  N.NH.C6H5  +  NH3  +  C6H5NH2. 

— C.CH  =  N.NH.C6H5 
— CO.CH  =  N.NH.C6H5  +  NH2.NH.C6H5  ->      ||  +  H20. 

N.NH.C6H5 

Many  of  the  simpler  sugars  react  after  this  manner,  forming  osazones, 
which  have  a  characteristic  appearance  under  the  microscope,  and  are  of 
special  value  for  identification  purposes. 

Preparation  246. — Glucosazone. 

C4H5(OH)4.CNNH.C6H5.CH.N.NHC6H5,       C18H22N404.  358. 

2  gms.  of  glucose  are  dissolved  in  10  c.cs.  water  and  a  solution  of  4  gms. 
phenylhydrazine  in  4  gms.  glacial  acetic  acid  and  10  c.cs.  water  is  added. 
The  mixture  is  heated  on  the  water  bath  for  90  minutes,  when  the  yellow 
osazone  separates  out.  It  is  filtered,  washed  with  water,  and  recrystallised 
from  alcohol. 

Yield.— 2  gms.  Golden  yellow  needles  ;  M.P.  204°.  (B.,  17,  579  ; 
20,  821.) 

Preparation  247.  —  Acetone  Phenylhydrazone  (2-Propan-phenyl- 
hydrazone). 

(CH3)2C  =  N.NHC6H5.       C9H12N2.  148. 

1  volume  of  glacial  acetic  acid  is  added  to  phenylhydrazine  (1  mol.). 
The  solution  is  diluted  with  2  volumes  of  water,  and  acetone  (1  mol.) 
is  added.  The  acetone  phenylhydrazone  which  separates  is  extracted 
with  ether.  The  latter  is  separated,  dried  over  anhydrous  potassium 
carbonate,  and  distilled  under  reduced  pressure,  the  fraction  165°  at 
91  mms.  being  retained.  The  oil  still  contains  traces  of  ammonia,  but  this 
may  be  removed  by  allowing  to  stand  in  a  vacuum  desiccator  over 
sulphuric  acid  for  a  short  time. 

(CH3)2CO  +  H2N.NH.C6H5  ->  (CH3)2C  =  N.NH.C6H5  +  H20. 

Yield. — Theoretical.  Colourless,  somewhat  unstable  oil;  B.P.91  165°. 
(B.,  16,  662.) 

Preparation  248. — Phenylhydrazone  of  Pyruvic  Acid  (Phenylhydrazone 
of  2-oxy-propan  acid). 

CH3C:N.NHC6H5. 

I  C9H10O2N2.  178. 

COOH. 

5  gms.  (2  mols.)  of  phenylhydrazine  are  dissolved  in  5  gms.  (excess) 
of  glacial  acetic  acid  and  5  c.cs.  of  water  added.    2  gms.  (1  mol.)  of  pyruvic 


284  SYSTEMATIC  ORGANIC  CHEMISTRY 


acid  are  added,  and  the  mixture  shaken.  The  precipitate,  after  filtration, 
is  washed  with  dilute  acetic  acid.    It  may  be  recrystallised  from  alcohol. 

CH3.CO.COOH  +  H2N.NH.C6H5  =  CH3.C:  (N.NHC6H5)COOH  +  H20. 

Yield. — Theoretical  (4  gms.).  Yellow  needles  ;  M.P.  192°  (the  substance 
must  be  heated  quicklv,  as  it  decomposes  somewhat  below  its  melting 
point).    (J.  pr.  [2],  52,  39  ;  B.,  16,  2241.) 

The  following  modification  of  the  reaction  is  of  interest : — 

Preparation  249. — l-Phenyl-3-methyl-pyrazolone. 

N  N.C6H5 

I        ^>CO  C10H10ON2.  174. 

CH3C  CHo 

13-5  gms.  of  ethyl  acetoacetate  are  added  to  10  gms.  of  phenylhydrazine 
and  vigorously  shaken.  The  oil  thus  obtained  is  removed  and  heated  on 
the  water  bath  for  about  2  hours  until  a  test  portion  solidifies  when  treated 
with  ether.  A  little  ether  is  poured  into  the  warm  liquid,  the  white 
crystals  which  separate  being  washed  with  ether  and  dried  at  100°.  The 
product  is  recrystallised  from  hot  water  or  alcohol. 

N — NHC6H5 

CH3.CO.CH2.CO.OC2H5  +  H2N.NH.C6H5    =  ||  +  H20. 

CH3C.CH2.C02C2H5 
N  NHC6H5  N  N(C6H5) 

=  CO  +  C2H5OH. 

I 

CH3.C.CH2.CO.OC2H5       CH3.C  CH2 

Yield. — Theoretical  (16  gms.).  White  crystals  ;  almost  insoluble  in 
cold  water,  ether,  and  ligroin  ;  fairlv  soluble  in  hot  water  ;  easily  soluble 
in  alcohol ;  M.P.  127°.    (B.,  16,  2597.) 

Reaction  CXXIX.   Action  of  Semicarbazide  on  Aldehydes  and  Ketones. 

Most  aldehydes  and  ketones  condense  readily  with  semicarbazide,  yielding 
semicarbazones. 

E.CHO  +  NH2.NH.CO.NH2  ->  ECH  :  N.NH.CO.NH2  +  H20. 

The  operation  is  usually  carried  out  as  follows  : — 

Semicarbazide  hydrochloride  (1  mol.)  is  dissolved  in  the  minimum 
quantity  of  cold  water  ;  sodium  or  potassium  acetate  (1  mol.)  is  dissolved 
in  96%  alcohol,  and  to  a  mixture  of  these  two  solutions  the  aldehyde  or 
ketone  (1  mol.)  is  added.  The  semicarbazone  separates  at  once,  or  on 
standing. 

Phenylsemicarbazide  reacts  similarly. 
Preparation  250. — Benzaldehyde  Semicarbazone. 

C6H5CH  =  N.NH.CO.NH2.       C8H9ON3.  163. 

13  gms.  of  hydrazine  sulphate  are  dissolved  in  100  c.cs.  of  water  and 
neutralised  by  the  gradual  addition  of  5-5  gms.  anhydrous  sodium  car- 


THE  LINKING  OF  NITROGEN  TO  CARBON 


285 


bonate.  After  cooling,  8-5  gms.  potassium  cyanate  are  added,  and  left 
to  stand  overnight.  The  solution  is  then  acidified  with  acetic  acid  and 
filtered.  The  filtrate  is  treated  with  10  gms.  benzaldehyde  and  placed  in  a 
mechanical  shaker  for  30  minutes.  It  is  then  allowed  to  stand  overnight. 
Benzaldehyde  semicarbazone  separates  out  in  almost  theoretical  yield, 
and  is  filtered  off  and  recrystallised  from  aqueous  alcohol. 

2N2H4H2S04  +  Na2C03  ->  2N2H4HS04  +  Na2S04  +  H2C03. 
(NH2.NH2)HS04  +  KCNO  — >  NH2NHCONH2  +  KHS04. 
NH2.NH.CO.NH2  +  C6H5CHO  ->  C6H5CH  :  N.NH.CO.NH2  +  H20. 

M.P.  about  214°  with  decomposition. 

Benzaldehyde  semicarbazone  may  also  be  obtained  in  theoretical  yield 
by  agitating  benzaldehyde  (1  mol.)  with  an  aqueous  solution  of  semi- 
carbazide  hydrochloride  (1  mol.).    (A.,  270,  34  ;  B.,  27,  32.) 

Peeparation  251. — Acetone  Semicarbazone. 

(CH3)2C  =  N.NH.CONH2.       C4H9ON3.  115. 

25  gms.  of  semicarbazide  hydrochloride  are  dissolved  in  a  small  quantity 
of  water ;  to  this  a  solution  of  21  -8  gms.  of  potassium  acetate  in  a  small 
quantity  of  alcohol  is  added.  The  mixed  solutions  are  well  shaken  and 
cooled  in  ice  in  order  to  precipitate  as  much  of  the  potassium  chloride  as 
possible,  and  then  filtered.  To  the  nitrate  12-9  gms.  of  acetone  are  added 
and  the  solution  allowed  to  stand  overnight.  The  precipitated  acetone 
semicarbazone  is  filtered  off.  If  more  acetone  is  added  to  the  filtrate 
further  precipitation  occurs.    It  is  then  recrystallised  from  hot  alcohol. 

CH  CH 

3X\C  =  0  +  H2N.NH.CONH2  ->        3N>C  =  N.NH.CONH2  +  H20. 
CH/  OH/ 

Yield. — 95%  theoretical  (24  gms.).  M.P.  188°— 189°  with  decom- 
position.   (A.,  283,  19.) 

Reaction  CXXX.  Formation  o£  Amino  Guanidine  Derivatives. — Amino 
guanidine  combines  with  aldehydes  and  ketones  in  presence  of  a  mineral 
acid. 

KRjCO  +  NH2.NHV 

>C  :  NH  ->  RR1C  =  N.NHX 
NH/  >C  :  NH  +  H,0, 

NH/ 

Many  of  the  resulting  compounds  form  crystalline  picrates,  and  are 
isolated  as  such.  The  compounds  with  aromatic  aldehydes  are  isolated 
as  difficultly  soluble  nitrates. 

Reaction  CXXXI.  Formation  of  Semioxamazones. — Semioxamazide, 
NH2.CO.CO.NH.NIT2  possesses  similar  properties  to  semicarbazide,  and 
reacts  well  with  aldehydes,  but  with  ketones  the  reaction  does  not  seem 
to  be  generally  applicable. 

R.CHO  +  H2N.NH.CO.CO.NH2  ->  R.CH  :  N.NH.CO.CO.NH2  +  H20. 
The  aldehydes  or  ketones  and  the  semioxamazide  are  weighed  in  mole- 


286 


SYSTEMATIC  ORGANIC  CHEMISTRY 


cular  proportions,  and  when  the  former  are  insoluble  in  water  it  is  best  to 
dissolve  them  in  a  small  quantity  of  alcohol.  The  semioxamazide, 
dissolved  in  the  minimum  quantity  of  water,  is  then  added  and  the 
mixture  thoroughly  shaken  for  some  time,  when  a  precipitate  of  the  semi- 
oxamazone  separates.  The  semioxamazones  are  usually  white  powders 
of  definite  melting  point,  sparingly  soluble  in  the  usual  organic  solvents 
and  insoluble  in  water.    (See  also  J.  C.  S.,  123,  394.) 

Reaction  CXXXII.  Action  of  Aliphatic  Halogen  Compounds  on  Aliphatic 
or  Aromatic  Primary  Amines. — Secondary,  tertiary  and  quaternary 
compounds  may  be  formed. 

EiCl                   EiCl  EjCl 
E.NH2  >  E.NHEX  >  ENfE^  >  EN(E1)3C1. 

In  this  way  secondary  and  tertiary  amines  may  be  obtained  from 
primary.  Quaternary  compounds  are  obtained  by  prolonged  action  of 
an  excess  of  halogen  compound  on  primary  amines,  or  more  usually  by 
the  action  of  halogen  compound  on  a  tertiary  amine. 

Preparation  252. — Dimethyl-benzyl-phenyl-ammonium  chloride  (Meth- 
chloride  of  methyl-benzyl-phenyl  amine). 

N(CH8)2(CH2.CeH6)(C6H6).Cl.       C15H18NC1.  247-5. 

A  mixture  of  5  gms.  (1  mol.)  of  dimethyl  aniline  and  5-3  gms.  (1  mol. 
of  benzyl  chloride  is  placed  in  a  basin,  which  is  left  in  a  desiccator  at 
ordinary  temperature  for  2 — 3  months.  At  the  end  of  this  time  the  mass 
is  practically  solid  ;  it  is  pressed  out  on  porous  plate,  washed  with  ether 
and  recrystallised  from  water  or  alcohol. 

C6H5N(CH3)2  +  C6H5CH2C1  ->  N(CH8)a(CHaC6H5)(C6H5)Cl.  ' 

Yield. — Theoretical  (10  gms.).  Colourless  plates,  containing  l.Ho0 
of  crystallisation  ;  M.P.  110°.    (B.,  10,  2079.) 

Preparation  253. — Trimethyl- ft -naphthyl-ammonium  iodide  (Meth- 
iodide  of  dimethyl-/3-naphthylamine). 

C10H7N(CH8)2I.       C13H16NI.  313. 

5  gms.  (1  mol.)  of  f$  naphthylamine,  20  gms.  (excess)  of  methyl  iodide, 
and  20  c.cs.  of  water  are  placed  in  a  flask  and  boiled  under  reflux  until 
the  amine  completely  dissolves  (about  3  hours).  The  quaternary  com- 
pound formed  separates  out  on  cooling.  It  is  filtered  off,  washed 
sparingly  with  water,  and  dried  on  porous  plate. 

C10H7NH2  +  3CH3I  ->  C10H7N(CH3)3I  +  2HI. 

Yield. — Theoretical  (12  gms.).    Colourless  needles  ;  decompose  when 
heated  or  exposed  to  air.    (B.,  11,  638  ;  13,  2054.) 
Preparation  254.— Pyridine  Methiodide. 

C5H5NCH3.I.       C6H8NL  221. 

1  c.c.  of  pyridine  and  1  c.c.  of  methyl  iodide  are  mixed  with  a  glass 
rod  in  a  small  test  tube.    A  vigorous  reaction  sets  in  and  product  becomes 


THE  LINKING  OF  NITROGEN  TO  CARBON  287 


very  hot.  After  a  few  minutes,  5  c.es.  absolute  alcohol  are  added,  and 
gently  warmed  to  dissolve.  On  cooling,  the  product  crystallises  out  in 
flat  needles,  which  are  filtered  off  and  washed  with  a  little  alcohol. 


h  CH3I  -5 

N  N 
CH3XI 

M.P.  117°.    (B.,  18,  3438.) 

Following  are  developments  and  modifications  of  the  present  reaction  : — 
Preparation  255.— Methyl  Aniline  (Phenyl-methylamine). 

C6H5NH.(CH3).       C7H9N.  107. 

20  gms,  (1  mol.)  of  acetanilide  (see  p.  296),  5  gms.  (excess)  of  sodium 
wire,  and  100  gms.  of  pure  xylene  (dried  over  sodium)  are  refluxed  for 
2 — 3  hours  in  an  oil  bath  at  130°.  After  cooling,  15  gms.  (rather  more 
than  theoretical)  of  methyl  iodide  are  added,  and  the  mixture  digested 
for  a  short  time  until  no  more  methyl  iodide  condenses  in  the  condenser 
tube.    The  xylene  is  then  distilled  off. 

The  methyl  acetanilide  is  boiled  with  concentrated  alcoholic  potash 
solution  for  about  24  hours  in  a  reflux  apparatus.  The  alcohol  is  distilled 
off,  and  the  residue  neutralised  by  addition  of  hydrochloric  acid.  The 
residual  xylene  is  then  distilled  ofi  in  steam,  the  solution  made  alkaline, 
and  the  methylaniline  steam-distilled.  It  is  taken  up  with  ether,  dried 
over  fused  sodium  sulphate  or  potassium  hydroxide  and  fractionated. 

C6H5NH.COCH3  +  CH3I  ->  C6H5N.(CH3)CO.CH3  ->  C6H5NH.CH3. 

Yield.— Theoretical  (15  gms.).  Yellowish  oil ;  B.P.  192°  ;  D.1,5  0-976. 
(B.,  10,  328=) 

In  certain  cases  addition  of  sodium  carbonate  is  effective. 
Preparation  256. — Dimethyl-o-toluidine. 

/N(CH3)2 

C6H<  C9H13N.  135. 

*XCH3. 

15  gms.  o-toluidine,  42  gms.  methyl  iodide  and  16  gms.  sodium  carbonate 
dissolved  in  250  c.cs.  water  are  heated  in  a  reflux  apparatus  on  a  water 
bath  for  about  2  hours  until  methyl  iodide  no  longer  condenses  in  the 
condenser  tube.  The  liquid  is  then  made  strongly  alkaline  with  caustic 
soda  solution  ;  the  amine  is  extracted  with  ether,  the  extract  dried  over 
solid  potash  and  distilled.    The  amine  comes  over  at  175° — 185°. 

/NH2  yN(CH3)2 
C6H4<         +  2CH3I  +  Na2C03  ->  C6H4<  +  2NaI  +  H20  +  C02. 

XCH3  \CH3 

Yield.— 80%  theoretical  (15  gms.).  Pale  yellow  liquid  ;  B.P.  183°. 
B.,  24,  563.) 


288  SYSTEMATIC  ORGANIC  CHEMISTRY 


The  following  preparation  is  of  interest  in  connection  with.  Fischer's 
researches  on  the  proteins  : — ■ 

Preparation  257.  —  Leucyl-glycine  (  { 5-Methyl-l-oxy-2-amino-l- 
pentanyl}  amino  ethan  acid). 

(CH3)2 :  CH.CH2.CH(NH2).CO.       C8H1603N2.  188. 
HOOC.CH2.NH. 

10  gms.  (1  mol.)  of  glycocoll  are  dissolved  in  133  c.cs.  (1  mol.)  of  normal 
caustic  soda,  and  while  cooled  with  ice  and  vigorously  shaken,  the  solution 
is  treated  alternately  with  170  c.cs.  (excess)  of  cold  N.  caustic  soda,  and 
37  gms.  (1  mol.)  of  a-bromisocapronyl-bromide  (C.  1910,  I.  1345)  in  four 
portions,  each  new  addition  being  made  only  when  the  smell  of  the  acid 
bromide  has  disappeared.  The  whole  operation  lasts  about  20  minutes. 
The  liquid  is  filtered  from  the  small  amount  of  oil  it  contains,  and  then 
treated  with  35  c.cs.  (excess)  of  5N.  hydrochloric  acid.  The  oil  which  is 
precipitated  is  extracted  with  ether,  and  the  condensation  product  pre- 
cipitated from  the  ethereal  solution  after  the  latter  has  been  concen- 
trated, by  the  addition  of  a  large  quantity  of  petroleum  ether.  The  pro- 
duct a-bromisocapronyl-glycine  soon  crystallises.  It  is  filtered  at  the 
pump,  washed  with  petroleum  ether,  and  recrystallised  from  hot  water, 
or  from  chloroform. 

(CH3)2 :  CHCH2CHBrCOBr  +  NH2CH2COOH  = 
(CH3)2:  CHCH2CHBr.CO.NH.CH2COOH  +  HBr. 

Yield.— 75%  theoretical  (26  gms.).    Colourless  crystals  ;  M.P.  133°. 

The  chief  fraction  of  the  raw  product  can  also  be  obtained  in  crystalline 
form  at  once  if  the  alkaline  solution  is  first  made  slightly  acid,  treated  with 
a  few  crystals  previously  prepared,  and  then  continually  stirred  while 
the  rest  of  the  hydrochloric  acid  is  slowly  poured  into  it. 

The  a-bromisocapronyl-glycine  is  converted  into  leucyl-glycine  by 
dissolving  it  in  5  times  its  weight  (excess)  of  25%  ammonia  (D.  0*910), 
and  allowing  the  solution  to  stand  for  4  days  at  room  temperature.  The 
crystalline  paste  of  ammonium  bromide  and  dipeptide,  which  is  produced 
when  the  solution  is  concentrated  on  a  water  bath,  is  treated  with  absolute 
alcohol  and  again  evaporated.  The  residue  is  boiled  with  alcohol,  and 
when  cold  the  leucyl-glycine,  which  is  insoluble  in  alcohol,  is  filtered  off 
at  the  pump  and  washed  with  alcohol  until  a  sample  of  it  dissolved  in 
water  gives  no  further  precipitate  with  silver  nitrate.  The  dipeptide  is 
purified  by  dissolving  it  in  15  times  its  weight  of  hot  water.  On  cooling, 
about  half  the  product  separates  out  in  crystalline  form.  By  concen- 
trating the  mother  liquor  and  precipitating  with  alcohol,  the  rest  may  be 
obtained.    The  product  should  be  free  from  bromine. 

(CH3)2 :  CH.CH2CHBr.CO.NH.CH2.COOH  +  2NH3  = 
(CH3)2:  CH.CH2CH(NH2).CO.NH.CH2.COOH  +  NH4Br. 

Yield. — 80%  theoretical  (6  gms.  for  each  10  gms.  of  the  a-bromiso- 
capronyl-glycine taken).  Colourless  crystals  ;  soluble  in  water  ;  insoluble 
in  alcohol ;  M.P.  (decomposition)  243°.    (B.,  42,  3398 ;  C,  1909,  II.,  1546.) 


THE  LINKING  OF  NITROGEN  TO  CARBON 


289 


Reaction  C XXXIII.  Action  of  Aromatic  Halogen  Compounds  on 
Ammonia  or  Amino  Compounds. — While  aliphatic  halides  readily  react 
with  ammonia  and  amines  according  to  Reaction  CXXXII,  the  halogen  of 
aromatic  halides  is  but  slightly  reactive,  unless  a  number  of  negative 
groups  (e.g.,  nitro)  are  also  present  in  the  molecule.  It  is  found,  however, 
that  the  addition  of  copper  powder  or  cuprous  halide  greatly  accelerates 
the  elimination  of  halogen  hydride  when  aromatic  halides  and  amino 
compounds  interact. 

Pkepakation  258. — Diphenylamine  (Phenyl-aniline). 

C6H5NHC6H5.       C12HnN.  169. 

10  gms.  (1  mol.)  of  acetanilide,  5  gms.  of  dry  potassium  carbonate, 
20  gms.  (excess)  of  brom-benzene,  and  a  little  cuprous  iodide  in  nitro- 
benzene solution,  are  remixed  for  15  hours.  The  dark-brown  liquid 
is  then  steam-distilled  until  no  more  nitrobenzene  passes  over.  The 
residue  in  the  distillation  flask,  consisting  of  the  acetyl  derivative  of 
diphenylamine,  is  a  thick  brown  oil.  It  is  dissolved  in  ether,  filtered, 
dried  over  calcium  chloride,  and  the  ether  removed  on  a  water  bath.  The 
residue  is  crystallised  from  alcohol,  from  which  it  separates  as  white 
plates,  melting  at  102°. 

The  crystals  are  dissolved  in  30  c.cs.  of  alcohol,  and  hydrolysed  by  boiling 
with  30  c.cs.  of  cone,  hydrochloric  acid  for  2 — 3  hours.  The  product  is 
distilled  in  steam,  a  yellow  oil  passing  over,  which  solidifies  in  the  con- 
denser. 

C6H5NHCOCH3  +C6H5Br-^  (C6H5)2N.COCH3^(C6H5)2NH  +  CH3COOH. 

Yield.- — 60%  theoretical  (7-5  gms.).    Yellow  plates  ;   soluble  in  hot 
alcohol ;  M.P.  53° ;  B.P.  310°.    (B.,  40,  4543.) 
Pkepakation  259. — Phenylglycine-o-carboxylic  Acid. 

/NH.CH2.COOH 
C6H4<  C9H904N.  195. 

\COOH. 

20  gms.  potassium-o-chlorbenzoate  (prepared  from  the  free  acid  and 
caustic  potash),  5-5  gms.  solid  caustic  potash,  7  gms.  potassium  carbonate, 
7-5  gms.  glycocoll,  15  c.cs.  water,  and  a  small  quantity  of  copper  powder 
are  placed  in  a  flask  provided  with  a  reflux  condenser.  The  mixture 
is  heated  to  boiling  in  an  oil  bath  for  an  hour,  the  contents  finally  becoming 
yellow  in  colour.  The  product  is  cooled  somewhat,  and  boiling  water 
added  to  redissolve  the  crystals  which  have  separated.  The  solution 
is  filtered  and  the  filtrate,  while  hot,  treated  with  excess  of  hydrochloric 
acid  ;  phenylglycine  o-carboxylic  acid  separates,  and  after  some  time  is 
filtered  off  and  recrystallised  from  water. 

.CI  /NH.CH2.COOH 
C6H4<  +  H2N.CH2COOH  ->  C6H4< 

\COOK  \COOH 

Yield. — Practically  theoretical  (19  gms.).  M.P.  200°  (with  decomposi- 
tion).   (D.R.P.,  142507.) 


290 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Reaction  CXXXIV.   Action  of  Silver  Cyanide  on  Alkyl  Halides. 

EX  +  AgNC  ->  RNC  +  AgX. 

Isocyanides  (isonitriles  or  carbylamines)  are  formed  in  this  reaction, 
which  is  illustrated  in  the  following  : — 

Preparation  260. — Ethyl  Isocyanide  (Ethyl-carbylamine). 

C2H5.NC.       C3H5N.  55. 

20  gms.  (1  mol.)  of  ethyl  iodide  are  gently  renuxed  in  a  fume  cupboard 
under  a  long  condenser  with  30  gms.  (excess)  of  dry  silver  cyanide  until 
the  liquid  ceases  to  drip  back,  and  the  mass  is  pasty  (about  1  hour). 
A  soluble  crystalline  compound  ethyl  argento -cyanide,  C2H5Ag(NC)2, 
is  now  contained  in  the  flask.  Ethyl  isocyanide  is  formed  from  it 
either  by  heating  it  to  180°,  or  better,  by  heating  to  100°  with  concen- 
trated potassium  cyanide  solution.  A  solution  of  10  gms.  (1  mol.) 
powdered  98%  potassium  cyanide  in  25  c.cs.  of  water  is  added,  and  the 
contents  of  the  flask  distilled  from  a  water  bath  in  a  fume  cupboard,  the 
distillate  being  collected  in  a  flask  with  an  outlet  to  a  good  draught  pipe. 
It  is  redistilled  with  the  same  precautions,  the  fraction  75° — 78°  being 
separately  collected. 

C2H5I  +  2 AgNC  -  C2H5Ag(NC)2  +  AgL 
C2H5Ag(NC)2  +  KNC  =  KAg(NC)2  +  C2H5NC. 

Volatile  liquid  ;  very  offensive  odour  ;  B.P.  78°.    (J.  pr.  [2],  30,  319.) 
Reaction  CXXXV.   Action  of  Chloroform  and  Alcoholic  Potash  on 
Aliphatic  and  Aromatic  Primary  Amines. 

E.NH2  +  CHC13  +  3KOH  ->  R.NC  +  3KC1  +  3H20. 

Isonitriles  are  formed.  The  reaction  is  convenient  for  the  detection 
of  primary  amines  ;  the  isonitriles  have  a  characteristic,  but  poisonous, 
odour ;  the  operation  should,  therefore,  be  conducted  in  a  good  draught 
cupboard. 

Reaction  CXXXVI. — Action  of  the  Hydrochloride  of  a  Primary  Aromatic 
Base  on  the  Base. 

R.NH2  +  HC1.NH2R  ->  R.NH.E  +  NH4C1. 

The  reaction  takes  place  at  a  high  temperature  and  usually  under  high 
pressure  in  an  autoclave,  secondary  amines  being  formed. 
Preparation  261. — Diphenylamine. 

<(  )-NH-(  ^>       C12HnN.  169. 

93  gms.  aniline  and  93  gms.  aniline  hydrochloride  are  heated  for 
20  hours  to  230°  in  an  enamelled  autoclave,  the  pressure  reaching 
about  6  atms.  No  iron  should  be  in  contact  with  the  reaction  products, 
else  the  yield  is  reduced.  After  2  hours,  the  water  present  is  cautiously 
blown  off  through  the  valve,  this  process  being  repeated  three  times 
during  an  hour.    The  presence  of  water  has  a  very  marked  influence  on 


THE  LINKING  OF  NITROGEN  TO  CARBON 


291 


the  reaction.  Some  aniline  and  ammonia  also  escapes.  The  reaction 
is  complete  after  about  20  hours.  The  contents  of  the  autoclave  are  then 
placed  in  a  porcelain  basin  with  a  litre  of  water,  and  heated  to  80°.  70  c.cs. 
strong  hydrochloric  acid  are  added  until  the  reaction  is  just  acid  to  Congo 
Red.  It  is  then  allowed  to  cool.  After  several  hours  the  crude  diphenyl- 
amine  separates  as  a  solid  cake,  which  can  easily  be  removed  from  the 
mother  liquor.  It  is  then  melted  under  a  little  water,  and  any  unchanged 
aniline  extracted  with  a  little  hydrochloric  acid,  and  washed  with  dilute 
sodium  carbonate.  The  diphenylamine  is  then  purified  by  distilla- 
tion with  superheated  steam  (see  p.  23),  the  temperature  of  the  oil 
bath  being  250°,  and  that  of  the  superheated  steam  300°.  The  diphenyl- 
amine is  obtained  as  an  almost  colourless  liquid,  which  solidifies  to  a 
pale-yellow  cake. 

Aniline  can  be  recovered  from  the  acid  mother  liquors. 

)NH2  +  HC1.NH2^      /        \      )-NH-(      ^>  +  NH4C1. 

Yield. — 60%  theoretical  (100  gms.).  Colourless  crystals  ;  peculiar 
smell ;  M.P.  53°  ;  B.P.  310°  ;  important  intermediate  for  dyestuffs. 
(B.,  40,  4541.) 

Reaction  C XXXVII.  Action  of  Bromine  (or  Chlorine)  and  Alkali  on 
Certain  Amides  and  Imides  (Hofmann's  Reaction). — This  method  is 
applicable  for  the  preparation  of  both  aliphatic  and  aromatic  amines. 

E.CO.NH2  +  Br2  — >  R.CO.NHBr  +  HBr. 
R.CO.NHBr  ->  R.N  :  CO  +  HBr. 
RNCO  +  H20  ->  R.NH2  +  C02. 

The  reaction  proceeds  in  stages,  a  bromamide  being  first  formed  ;  this 
loses  a  molecule  of  hydrogen  bromide  on  further  action  with  caustic 
soda,  yielding  probably  an  isocyanate,  which,  being  unstable  in  presence 
of  excess  of  alkali,  is  hydrolysed  to  an  amine  and  carbon  dioxide. 
Sodium  hypochlorite  (or  hypobromite)  and  sodium  hydroxide  are  the 
reagents  used.  The  reaction  finds  industrial  application  in  the  prepara- 
tion of  anthranilic  acid  for  the  synthesis  of  indigo.  On  a  technical  scale 
sodium  hypochlorite  is  always  employed,  but  on  a  small  scale  sodium 
(or  potassium)  hypobromite  is  frequently  used  owing  to  the  ease  with 
which  a  solution  of  known  strength  can  be  made  up  from  weighed 
quantities  of  bromine  and  alkali. 

Preparation  262. — Anthranilic  Acid  (Ortho-amino-benzoic  acid). 

NH2 

C6H4<  C7H702N.  137. 

\COOH 

40  gms.  of  finely  powdered  phthalimide  and  80  gms.  of  caustic  soda  are 
dissolved  together  in  280  c.cs.  of  water,  the  solution  being  cooled  during 
the  operation.  The  solution  is  agitated,  and  400  gms.  of  a  5%  solution 
of  sodium  hypochlorite  run  in.  When  all  is  added,  the  solution  is  warmed 
for  a  few  minutes  at  80°  to  complete  the  reaction  ;  it  is  then  cooled  and  neu- 
tralised exactly  with  hydrochloric  or  sulphuric  acid.    An  excess  of  strong 

u  2 


292 


SYSTEMATIC  ORGANIC  CHEMISTRY 


acetic  acid  is  added  to  precipitate  the  anthranilic  acid,  which  is  filtered 
off  and  washed  with  water.  Any  anthranilic  acid  remaining  in  the 
filtrate  is  precipitated  as  copper  anthranilate  by  the  addition  of  a  saturated 
solution  of  copper  acetate.  After  standing  for  some  time  the  precipitate 
is  filtered  off  and  suspended  in  a  small  quantity  of  warm  water,  while  a 
current  of  sulphuretted  hydrogen  is  passed  into  the  suspension.  The 
copper  sulphide  formed  is  filtered  off,  and  anthranilic  acid  recovered  from 
the  filtrate  by  concentration  on  a  water  bath.  It  may  be  recrystallised 
from  hot  water. 

/C0X  yNH2 

C°H<C0>H^C'H<C00H. 

Total  Yield.— 85%  theoretical  (31-5  gms.).  M.P.  145°  (D.R.P., 
55988  ;  J.  Soc.  Dyers,  1901,  17,  139.) 

Reaction  CXXXVIII.  Action  of  Heat  on  Ammonium  Salts. — Ammo- 
nium salts  of  monobasic  acids  yield  amides. 

R.COONH4  ->  R.CO.NH2  +  H20. 

While  those  of  dibasic  acids  yield  imides. 

CH2.COOH  CH2.CCK 

|  ->     |  >NH  +  2H20.      .  ' 

CH2.CO.ONH4  CH2.C(K 

Peepaeation  263. — Acetamide. 

CH3CO.NH2.       C2H5ON.  59. 

20  gms.  ammonium  acetate  (as  dry  as  possible),  and  25  gms.  glacial 
acetic  acid  are  placed  in  a  small  round-bottomed  flask  provided  with 
a  reflux  condenser,  and  heated  to  gentle  boiling  over  a  wire  gauze  for 
3  hours.  The  flask  is  then  connected  by  means  of  a  cork  and  delivery 
tube  with  a  sloping  water  condenser  and  distillation  commenced.  The 
distillate  up  to  160°  is  discarded.  Above  160°  the  water  is  run  out  of 
the  condenser  and  the  distillate  collected  in  a  small  distilling  flask.  This 
portion  is  redistilled  and  the  fraction  210° — 225°  separately  collected ; 
it  solidifies  on  cooling  to  a  mass  of  white  crystals.  These  may  be  recrystal- 
lised from  ether  as  long  needles. 

CH3.COONH4  ->  CH3.CONH2  +  H20. 

Yield.—  80%  theoretical  (12  gms.).    M.P.  82°  ;  B.P.  222°.    (B.,  15, 
980.)    For  modification  of  above,  see  Am.  Soc.  44,  2286. 
Peepaeation  264. — Succinimide  (Imide  o£  butan-di  acid). 

CH2.COx 

I  )NH.       C4H502N.  99. 

CH2.CCK 

20  gms.  of  succinic  acid  are  dissolved  in  a  small  quantity  of  water  in  a 
basin,  and  the  solution  neutralised  with  ammonia.  The  solution  is 
boiled  to  expel  excess  of  ammonia,  after  which  a  further  20  gms.  of  succinic 


THE  LINKING  OF  NITROGEN  TO  CARBON 


293 


acid  dissolved  in  water  is  added.  The  solution  is  evaporated  to  complete 
dryness  on  a  water  bath  ;  the  dry  residue  is  transferred  to  a  retort  and 
heated  quickly  with  a  large  luminous  flame.  The  sublimate  of  succinimide 
is  recrystallised  from  pure  acetone. 


CH2COOH  CH2.C(X 

|  ->     j  )NH  +  2H20. 

CH2.COONH4  CH2.C(K 

Yield. — 70%  theoretical  (11  gms.).    Colourless  rhombic  plates  ;  M.P. 
126°  ;  B.P.  288°.    (A.,  49,  198.) 
Preparation  265. — Formamide  (Amide  of  formic  acid). 

H.CONH2.       CH3ON.  45. 

150  c.C3.  of  pure  formic  acid  are  placed  in  round-bottomed  flask  attached 
to  a  condenser,  and  having  also  a  delivery  tube  dipping  nearly  to  the 
bottom  of  the  acid  in  the  flask.  Dry  ammonia  gas  is  led  into  the  acid 
through  the  delivery  tube,  passing  first  through  a  tower  of  solid  caustic 
soda,  and  then  soda -lime.  Much  heat  is  evolved  during  the  reaction,  and 
the  flask  must  be  cooled.  -After  about  15  minutes  the  acid  is  neutralised, 
and  crystals  of  ammonium  formate  are  deposited.  The  flask  is  then 
heated  on  a  paraffin  bath,  and  at  150°  the  salt  begins  to  decompose  and 
water  passes  over.  The  temperature  is  gradually  raised  to  180°,  at 
which  temperature  no  more  water  distils  over.  The  resulting  brown 
liquid  is  distilled  under  greatly  reduced  pressure,  the  fraction  85° — 95° 
at  0-5  mm.  being  collected.  After  standing  over  anhydrous  sodium 
sulphate  for  some  days,  it  is  again  distilled  under  reduced  pressure. 

H.COONH4— H20  ->  H.CONH2. 

Yield. — 66%  theoretical  (98  gms.).  Viscous  colourless  liquid  ;  M.P. 
2-25°  ;  D.14  1-337.    (Am.  Soc,  40,  794.) 

Reaction  CXXXIX.  Action  of  Ammonia  on  Esters,  Acid  Chlorides  or 
Anhydrides. 

(1)  E.COOK!  +  NH3  ->  R.CO.NH2  +  R1OH. 

(2)  R.COC1  +  NH3  ->  R.CO.NH2  +  HC1. 


RCO, 
RCO- 


(3)  >0  +  2NH3  ->  2R.CO.NH2  +  H20. 


(1)  Is  restricted  mostly  to  esters  of  aliphatic  acids.  (2)  Is  employed  for 
the  preparation  of  aromatic  amides.  If  the  anhydride  of  a  dibasic  acid. 
e.g.,  phthalic,  is  employed,  an  imide  results. 

Preparation  266. — Acetamide. 

15  gms.  ethyl  acetate  are  treated  in  a  small  conical  flask  with  an  equal 
weight  of  cone,  ammonia  solution.  The  flask  is  corked  and  left  in  a  warm 
place  (say,  near  a  steam  bath)  until  the  two  layers  originally  present  give 
place  to  one  uniform  solution.  This  solution  is  then  distilled,  water, 
alcohol  and  ammonia  passing  over  up  to  100°  ;  the  fraction  210° — 225° 


294 


SYSTEMATIC  ORGANIC  CHEMISTRY 


is  separately  collected,  and  if  it  does  Dot  solidify  on  cooling  it  is  redistilled. 
The  final  product  is  recrystallised  from  ether. 

CH3.CO.OC2H5  +  NH3  ->  CH3.CONH2  +  C2H5.OH. 

Yield— 80%  theoretical  (8-5  gms.).  M.P.  82°.  (B.,  15,  981  ;  Am. 
Soc,  33,  974.) 

Oxamide  is  obtained  as  a  white  amorphous  precipitate  when  equal 
weights  of  dimethyl  (or  diethyl)  oxalate  and  cone,  ammonia  are  mixed. 
The  precipitate  is  filtered  off  and  recrystallised  from  alcohol. 

CH3O.OC.CO.CH3  +  2NH3  ->  NH2OC.CONH2  +  2H20. 

Peepaeation  267. — Benzamide. 

C6H5.CONH2.       C7H7ON.  121. 

10  gms.  finely  powdered  dry  ammonium  bicarbonate  are  placed  in  a 
mortar  in  a  fume  cupboard.  5  gms.  benzoyl  chloride  are  added  and  the 
whole  well  mixed  with  a  pestle  during  10  minutes.  If  the  odour  of  benzoyl 
chloride  persists  at  the  end  of  this  time,  a  few  drops  of  cone,  ammonia 
are  added.  The  product  is  diluted  with  water,  the  benzamide  filtered  off 
and  recrystallised  from  boiling  water. 

C6H5C0C1  +  2NH4HC03  ->  C6H5CONH2  +  NH4C1  +  2C02  +  2H20. 

Yield— 93%  theoretical  (4  gms.).  Glistening  plates;  M.P.  130°* 
(A,  3,  268 ;  B,  10,  1785.) 

Benzamide  may  also  be  prepared  by  adding  5  gms.  benzoyl  chloride 
drop  by  drop  to  20  c.cs.  cone,  ammonia  solution. 

Peepaeation  268. — Phthalimide. 

C6H4<^°\NH.       C8H502N.  147. 

20  gms.  phthalic  anhydride  are  placed  in  a  100-c.c,  conical  flask  fitted 
with  a  cork  carrying  inlet  and  exit  delivery  tubes.  The  flask  is  heated 
in  a  paraffin-wax  bath  until  the  anhydride  melts,  when  a  current  of  dry 
ammonia  is  led  in  through  the  inlet  tube,  which  reaches  to  within  1  cm. 
of  the  substance.  The  temperature  of  the  bath  is  gradually  raised  during 
an  hour  to  230°.  The  contents  of  the  flask  are  then  cooled  and  recrystal- 
lised from  ether. 

C6H4/  cQ ^0  +  NH3  ->  C6H4/  c(y>NH  +  H20. 

Yield.— 70%  theoretical  (14  gms.).    White  needles  ;  M.P.  232°  (A 
247,  294  ;  B.,  10,  579.) 
Reaction  CXL.   Action  of  Ammonia  on  Phenols  and  Sulphonic  Acids. 

(1)  K.OH+NH3     -^E.NH2  +  H20. 

(2)  K.S03H  +  NH8  ->  E.NH2  +  H2S03. 

(1)  Takes  place  readily  with  polyhydric  phenols  and  naphthols,  also  if 


THE  LINKING-  OF  NITROGEN  TO  CARBON 


295 


negative  groups  are  present  in  the  molecule,  e.g.,  nitrophenols  (B.,  19, 
2161). 

The  reaction  is  usually  carried  out  under  pressure,  and  the  yield  is 
improved  by  the  presence  of  sodium  or  ammonium  sulphite  (BuchererV 
method),  the  sulphurous  esters  of  phenols  reacting  more  readily  than 
phenols.  The  ammonia  is  used  in  the  form  of  its  concentrated  solution, 
or  as  its  addition  compound  with  zinc  chloride.  The  reaction  (2)  is  carried 
out  similarly  to  (1).  The  reaction  is  easy  in  the  anthraquinone  series,  but 
not  in  the  naphthalene  series,  where  sodamide  is  sometimes  used. 

R.S03H  +  NaNH2  ->  R.NH2  +  NaHS03. 

An  interesting  case  of  group  migration  may  be  mentioned  here 


(  y   0H  1  Y  i0H 

+  NaNH2  _> 

S chaffer's  acid.  NH2 

If  excess  NaNH2  is  used,  the  OH  group  is  also  replaced  by  NH2. 
Preparation  269. — /?-Naphthylamine  (2-Amido-naphthalene). 

C10H9N.  143. 

Method  I. — 144  gms.  /?-naphthol  and  600  gms.  ammonium  sulphite  are 
heated  in  an  autoclave  with  stirrer  and  oil  bath.  125  gms.  20%  ammonia 
are  also  added,  and  the  mixture  is  heated  for  8  hours  at  an  internal  tem- 
perature of  150°,  and  a  pressure  of  6  atms.  (Note. — No  brass  gauges 
should  be  used.)  The  contents  are  allowed  to  cool  and  the  cake  of 
^-naphthylamine  is  broken  up  and  thoroughly  washed  with  water  on  a 
filter.  After  washing  it  is  dissolved  in  1-|  litres  of  water  and  110  gms. 
hydrochloric  acid  (which  should  be  free  from  sulphuric  acid)  and  filtered. 
To  the  filtrate  is  added  about  400  gms.  saturated  sodium  sulphate 
solution  until  precipitation  of  the  naphthylamine  sulphate  is  complete 
(test).  It  is  then  filtered  and  washed  with  water.  The  free  base  is 
obtained  by  making  a  thin  paste  of  the  sulphate  and  heating  to  80°  with 
stirring,  when  caustic  soda  solution  is  added  until  the  liquid  gives  an 
alkaline  reaction  to  phenolphthalein.  It  is  then  filtered,  washed,  and 
dried  at  80°. 

+  NH3  -> 

\/\y  \/\/ 

Yield.— 85— 95%  theoretical  (120—135  gms.).  White  plates  ;  M.P. 
112°  ;  B.P.  294°  ;  the  sulphate  is  less  soluble  than  that  of  a  naphthyl- 
amine ;  important  intermediate  for  dyestuffs.  (E.P.,  1387,  1900 ; 
F.P.,  297464,  394820.) 

Method  II. — 50  gms.  ^-naphthol  and  200  gms.  powdered  zinc 
ammonia  chloride  are  mixed  and  heated  on  an  oil  bath  in  a  vessel 
provided  with  a  reflux  condenser  for  2  hours  at  200°.  The  product, 
after  cooling,  is  treated  with  25%  caustic  soda  solution  until  the 


296  SYSTEMATIC  ORGANIC  CHEMISTRY 


zinc  oxide  redissolves,  and  the  solution  boiled  for  a  few  minutes.  On 
cooling,  ^naphthylamine  separates.  It  may  be  removed  and  purified, 
as  described  in  Method  I.  It  may  also  be  separated  by  extraction  with 
ether,  or  by  distillation  in  a  current  of  superheated  steam.  (B.,  13,  1300.) 
Peepaeation  270. — 2-Amino-anthraquinone. 

/\/C0\/\NH, 

C14H902N.  223. 

\AC0/\/ 

20  gms.  sodium  anthraquinone  sulphonate  (silver  salt)  and  200  c.cs. 
of  cone,  aqueous  ammonia  (D.  0-88)  are  heated  in  an  autoclave  of  500  c.cs. 
capacity  to  180°,  and  maintained  at  this  temperature  for  6  hours.  The 
autoclave  is  left  to  cool  overnight,  then  opened,  and  the  amino  anthra- 
quinone filtered  off  and  dried. 

Red  crystals  ;  M.P.  302°.    (B.,  12,  1567.) 

Reaction  CXLI.  Action  of  Acids,  Acid  Anhydrides  and  Chlorides  on 
Primary  and  Secondary  Amines. — These  derivatives  are  usually  prepared 
by  treating  the  amine  with  the  organic  acid,  or  with  the  acyl  chloride  or 
anhydride.  When  the  acid  is  used  a  salt  is  first  formed  from  which  a 
molecule  of  water  is  eliminated  on  further  heating. 

ECOOH  +  EiNHa  ->  E-COONHgEj  ->  E-CONHEj  +  H20. 
ECOC1  +  RiNH2  — >  E.CONHEj  +  HC1. 
(ECO)20  +  2EXNH2  ->  2ECONHE,  +  H20. 

When  benzoyl  chloride  is  used  it  is  necessary  to  have  present,  or  to 
add  subsequently,  an  excess  of  caustic  soda  or  some  other  basic  substance 
(Schotten-Baumann  Reaction). 

When  an  acid  anhydride  is  used  the  reaction  is  usually  carried  out 
by  the  application  of  heat,  and  may  be  hastened  by  the  addition  of  dehy- 
drating agents,  e.g.,  fused  sodium  acetate  or  fused  zinc  chloride. 

Peeeaeatton  271. — Acetanilide  (Phenyl-amide  of  ethan  acid). 

A  mixture  of  25  gms.  (1  mol.)  of  redistilled  aniline  and  30  gms.  (excess) 
of  glacial  acetic  acid  is  boiled  under  an  air  condenser,  preferably  in  a  flask 
with  a  condenser  ground  into  the  neck,  until  no  aniline  separates  on  treating 
a  sample  with  a  cold  caustic  soda  solution  (8  hours).  The  hot  liquid  is 
at  once  poured  into  500  c.cs.  of  cold  water,  filtered,  and  washed  with  cold 
water.  The  crude  acetanilide  is  boiled  with  a  litre  of  water,  a  little  alcohol 
being  added  until  it  all  goes  into  solution.  It  is  filtered  through  a  hot 
water  filter  (see  p.  10),  and  the  solution  allowed  to  crystallise.  If  the 
product  is  dark  coloured,  it  is  redissolved  as  before,  boiled  with  5  gms.  of 
animal  charcoal  for  J  hour,  filtered,  and  allowed  to  crystallise. 

C6H5NH2  +  CHgCOOH  =  CH3CONHC6H5  +  H20. 

Yield. — 85%  theoretical  (30  gms.).  Rhombic  plates ;  sparingly 
soluble  in  hot  water  ;  M.P.  112°  ;  B.P.  295°.    (J.  C.  S.,  2,  106.) 

If  10  gms.  of  fused  sodium  acetate  (see  p.  506)  be  added  to  the 
reaction  mixture,  the  time  of  heating  can  be  shortened  to  6  hours.  An 


THE  LINKING  OF  NITROGEN  TO  CARBON 


297 


older  method  of  working  up  the  reaction  product  was  to  distil  fractionally 
the  mixture  of  acetanilide  and  excess  acetic  acid,  the  former  coming  over 
at  280°,  and  being  then  recrystallised  (A.  Ch.  [3],  37,  328). 

Preparation  272. — Benzanilide  (Phenylamide  of  benzene-carboxylic 
acid). 

C6H5NH.CO.C6H5.       C13HnON.  197. 

Method  I. — 12  gms.  of  aniline  are  placed  in  a  dish  in  a  fume  cupboard, 
and  10  gms.  of  benzoyl  chloride  are  gradually  added.  Much  heat  is 
developed.  When  cold  the  product  is  extracted  first  with  dilute  hydro- 
chloric acid  to  remove  aniline,  then  with  dilute  caustic  soda  to  remove 
benzoic  acid,  and  finally  with  water.  After  pressing  it  is  crystallised 
from  alcohol. 

C6H5.C0.C1  +  2C6H5NH2  ->  C6H5.CO.NH.C6H5  +  C6H5NH2.HC1. 

Yield.— Almost  theoretical  (20  gms.).    (A.,  60,  311.) 

In  the  above  process  only  one-half  of  the  amine  is  transformed  into  its 
benzoyl  derivative.  By  working  in  presence  of  dilute  caustic  soda  or 
other  alkali  (Schotten-Baumann  reaction,  see  benzoyl-£>-toluidide),  the 
amine  is  completely  converted  into  its  benzoyl  derivative. 

Method  II. — A  mixture  of  15  gms.  (1  mol.)  of  aniline,  and  20  gms. 
(1  mol.)  of  benzoic  acid  is  heated  in  a  retort  at  180°,  and  the  temperature 
raised  gradually  to  225°  ;  a  further  10  gms.  of  aniline  are  added,  and  the 
heating  continued.  The  hot  mass  is  then  poured  into  an  evaporating 
dish  and  allowed  to  solidify.  It  is  powdered,  washed  with  dilute  hydro- 
chloric acid  to  remove  unchanged  base,  then  with  water  to  remove  the 
benzoate,  then  with  dilute  caustic  soda  to  remove  free  acid,  and  finally 
with  water.    It  is  dried  and  crystallised  from  alcohol. 

C6H5NH2+  C6H5COOH  — >  C6H5NH2.C6H5COOH 
->  C6H5NHCOC6H5  +  H20. 

Yield. — 80%  theoretical  (26  gms.).  Colourless  plates  ;  insoluble  in 
water;  M.P.  162°.    (Bl.  [Ill]  11,  893.) 

Preparation  273. — Benzoyl-j>toluidide  (^-Tolyl-amide  oi  benzene 
carboxylic  acid). 

C6H5CONH.C6H4CH3[4.1].       C14H13ON.  211. 

2  gms.  (1  mol.)  of  finely  divided  ^-toluidine  are  mixed  with  10  c.cs.  of  a 
10%  aqueous  solution  of  sodium  hydroxide,  and  2  c.cs.  benzoyl  chloride 
(excess)  are  added  gradually  to  the  warm  mixture  in  a  corked  flask,  which 
is  mechanically  shaken.  Thorough  shaking  is  essential.  If  any  excess 
of  benzoyl  chloride  remains,  it  is  destroyed  by  warming  with  a  further 
quantity  of  sodium  hydroxide  solution.  The  mixture  is  then  poured  into 
water,  and  the  precipitate  filtered,  dried,  and  recrystallised  from  alcohol. 

CH3C6H4NH2  +  C6H5C0C1  +  NaOH=  C6H5CONHC6H4CH3  +  NaCl  +  H20. 

Yield. — Almost  theoretical  (4  gms.).  Colourless  crystals  ;  insoluble 
in  water  ;  M.P.  158°.    (B.,  19,  3219.) 


298  SYSTEMATIC  OKGANIC  CHEMISTRY 


Preparation  274. — Diacet-o-toluidide  (Di-ethanoyl  derivative  of  o- 
toluidine). 

CH3.C6H4N(CO.CH3)2[1.2].       CnH1302N.  191. 

10  gms.  of  o-toluidine,  38  gms.  of  acetic  anhydride  and  5  gms.  fused 
sodium  acetate  are  heated  to  boiling  for  1  hour  in  a  flask  provided  with 
an  air  condenser  and  calcium  chloride  tube.  After  this  time  the  product 
is  distilled  from  a  distilling  flask  at  a  pressure  of  20  mms.  Acetic  acid  and 
acetic  anhydride  pass  over  first ;  the  diacetyl  derivative  distils  at  152° — 
153°,  and  sodium  acetate  and  some  mono-acetyl  derivative  remain  in  the 
flask. 

CH3.C6H4NH2  +  (CH3CO)20  ->  CH3.C6H4N(COCH3)2  +  H20. 

Yield. — 80%  theoretical  (14  gms.).    Colourless  crystals  ;  somewhat 
unstable  ;  M.P.  18°.    (B.,  26,  2855.) 
Reaction  CXLII.   Action  of  Primary  Aromatic  Amines  on  Alcohols  — 

The  reaction  is  generally  carried  out  by  heating  under  pressure,  and  in 
presence  of  a  mineral  acid.    Secondary  and  tertiary  amines  are  formed. 

ENH2  +  RiOH  ->  RNHRi  +  H20. 
R.NHR!  +  RiOH  ->  RN(R1)2  +  H20. 

Preparation  275. — Dimethylaniline. 

C6H5N(CH3)2.       C9HUN.  133. 

93  gms.  pure  aniline,  105  gms.  pure  methyl  alcohol  and  9-4  gms.  cone, 
sulphuric  acid  are  heated  in  an  enamelled  autoclave  to  200°.  The  pressure 
rises  to  about  30  atms.,  and  the  contents  are  left  for  6  hours  at  215°. 
They  are  allowed  to  cool,  and  then  25  gms.  30%  caustic  soda  solution 
added.  The  product  is  now  heated  to  170°  in  the  autoclave  for  a  further 
5  hours.  This  second  heating  is  necessary  to  decompose  the  sulpho- 
ammonium  bases  formed,  and  which  are  decomposed  into  sulphuric  acid, 
alcohol,  and  tertiary  amine.  The  contents  of  the  autoclave,  after  cooling, 
are  distilled  in  steam.  The  dimethylaniline  is  salted  out  of  the  distillate 
with  common  salt.    It  is  then  separated  and  distilled. 


C6H5N 


H2    +  HO 
HO 


CH 

3 


CH?  CeH5N.(CHs)s 


Yield. — 95%  theoretical  (126  gms.).  Colourless  liquid  when  pure  ; 
turns  brown  on  standing  ;  B.P.  192°  ;  D.  0-96  ;  important  intermediate 
for  dyestuffs. 

Purity  Test  (anhydride  test). — Some  monomethylaniline  is  always 
present,  and  if  4  c.cs.  of  the  dimethylaniline  is  shaken  up  with  2  c.cs. 
acetic  anhydride,  this  should  not  give  an  increase  in  the  temperature  of 
more  than  1°  (C.  Z.,  34,  641). 

Preparation  276. — Diethylaniline. 

C6H5N(C2H5)2.       C10H15K  149. 

130  gms.  dried  aniline  hydrochloride  and  140  gms.  95%  alcohol  are 
heated  in  an  enamelled  autoclave  at  180°  for  8  hours.    After  cooling, 


THE  LINKING  OF  NITROGEN  TO  CARBON 


299 


the  contents  of  the  autoclave  are  placed  in  a  round-bottomed  flask  and 
the  alcohol  and  ethyl  ether  distilled  off.  The  residual  mixture  of  mono- 
and  diethylaniline  is  treated  with  110  gms.  30%  caustic  soda  solution. 
The  product  is  stirred  up  at  ordinary  temperature  with  40  gms.  of 
jy-toluene  sulphonic  chloride,  which  forms  a  non- volatile  derivative  with 
the  mono-ethyl  aniline.  The  diethylaniline  is  then  distilled  from  the 
mixture  in  steam,  and  separated  as  in  Preparation  275. 

The  mono-ethylaniline  can  be  obtained  by  hydrolysing  the  toluene 
sulphonic  derivative  with  cone,  sulphuric  acid. 

HOC2H*  ~*  CeH5N(C2H5)2. 


CH3/  _  _  ^S02C1  +  C2H5NH.C6H5  ->  CH,/  _  _^>S02.N<^ 


£s_0    CHs<f~     N>S03H  +  C2H5NH.C6H 


Yield. — 80%  theoretical  (120  gms.).  Colourless  liquid  when  pure  ; 
B.P.  216-5°  ; '  D.  0-939  ;  important  intermediate  for  dyestuffs.  (A..  74, 
128  ;  D.R.P.,  250236.) 

Reaction  CXLIII.  Condensation  of  Aromatic  Aldehydes  with  Primary 
Aromatic  Amines. — This  reaction  generally  takes  place  readily  on  heating. 

R.CHO  +  NHA  ->  RCH  =  NR1  +  HaO. 

Substituted  aldehydes  and  substituted  amines  also  react ;  for  example, 
the  sodium  salt  of  a-naphthylamine  4-sulphonic  acid  when  dissolved  in 
water  and  shaken  with  an  alcoholic  solution  of  benzaldehyde  yields 
sodium  benzylidine  naphthionate. 

With  aliphatic  aldehydes  the  reaction  takes  the  following  course  : — 

CH3.CHO  +  2NH2.C6H5  ->  CH3CH(NH.C6H5)2  +  H20. 

Formaldehyde  reacts  like  the  aromatic  aldehydes,  yielding  dihydro- 
formaldehyde  (or  methylene)  compounds. 

C6H5NH2  +  OCH2  ->  C6H5N  =  CH2  +  H20. 

Preparation  277. — Benzylidene  Aniline. 

C6H5N  =  CH.C6H5.       C13HnN.  181. 

9-3  gms.  of  aniline  (1  mol.)  and  10-6  gms.  of  benzaldehyde  (1  mol.) 
are  placed  in  porcelain  dish  on  a  water  bath  and  heated  for  an  hour. 
The  product,  while  still  warm,  is  poured  into  a  separating  funnel  previously 
warmed  in  a  steam  bath,  and  the  lower  layer  of  benzylidene  aniline 
separated  from  the  upper  layer  of  water.  The  product  can  be  used 
directly  for  the  preparation  of  ^-rdtraniline.  It  is  insoluble  in  water,  but 
can  be  recrystallised  from  alcohol. 

C6H5NH2  +  OCH.C6H5       C6H5N  =  CH.C6H5  +  H20. 

Yield,— Theoretical  (18  gms.).    M.P.  42°.    (J.,  1850,  488.) 


300  SYSTEMATIC  ORGANIC  CHEMISTRY 


Reaction  CXLXV.  Action  of  Ammonia  on  Aldehydes. — The  simplest 
case  is  the  formation  of  an  aldehyde  ammonia  by  the  action  of  dry 
ammonia  gas  on  the  aldehyde  in  dry  ethereal  solution.  Acetaldehyde 
and  several  of  the  aliphatic  aldehydes  react  after  this  fashion. 

R.CHO  +  NH3  ->  K.CHOH.NH2. 

Formaldehyde  and  most  of  the  aromatic  aldehydes  do  not  react  in  this 
way  with  ammonia,  but  form  complex  condensation  products. 
Peepakation  278— Acetaldehyde  Ammonia. 

CH3CHOHNH2.       C2H7ON.  61. 

Owing  to  the  easy  volatility  of  acetaldehyde  (B.P.  21°)  it  is  rather 
difficult  to  collect.  It  can,  however,  be  readily  absorbed  in  a  dry  ether 
contained  in  a  vessel  immersed  in  ice  water.  If  the  ethereal  solution  is 
now  saturated  with  dry  ammonia  gas,  colourless  crystals  of  aldehyde 
ammonia  separate,  which  are  filtered  off,  and  dried  either  by  exposure 
on  filter  paper  or  in  a  vacuum  desiccator.  As  aldehyde  ammonia  is  some- 
what soluble  in  ether  a  second  crop  may  be  obtained  by  concentrating  the 
mother  liquor.  If  the  ethereal  solution  of  aldehyde  is  moist  it  should  be 
dried  in  contact  with  anhydrous  sodium  sulphate,  and  decanted  before  the 
ammonia  is  passed  in. 

CH3CHO  +  NH3  ->  CH3CHOH.NH2. 

M.P.  70°— 80°  ;    B.P.  100°  ;    on  warming  with  dilute  acids  yields 
acetaldehyde  and  ammonium  salts.    (A.,  14,  133.) 
Preparation  279. — Hexamethylene  Tetramine  (Hexamine). 

(CH2)6N4.  140. 

50  c.cs.  of  "  formalin  "  containing  40%  formaldehyde  and  30  c.cs.  of 
cone,  ammonium  hydroxide  solution  (D.  0-88)  are  mixed  in  a  round- 
bottomed  flask.  The  flask  is  connected  to  a  suction  pump  and  the 
contents  evaporated  on  a  water  bath  under  diminished  pressure  to  a  thick 
paste.  A  second  equal  quantity  of  ammonium  hydroxide  is  then  added 
and  evaporated,  as  before.  The  residue  is  treated  with  sufficient  boiling 
absolute  alcohol  to  dissolve,  filtered  hot,  and  the  filtrate  set  aside  to  cool. 
Colourless  crystals  separate,  which  are  filtered  off  and  washed  with  a 
little  absolute  alcohol. 

6CH20  +  4NH4OH  ->  (CH2)6N4  +  10H2O. 

Sublimes  about  260°  ;  very  soluble  in  water.    (B./  19,  1842.) 
Preparation  280. — Hydrobenzamide. 

(C6H5CH)3N2.       C21H18N2.  298. 

5  c.cs.  of  benzaldehyde  and  25  c.cs.  cone,  ammonium  hydroxide  solution 
are  placed  in  stoppered  flask  and  allowed  to  stand  for  2  days.  Crystals 
of  hydrobenzamide  separate,  which  are  filtered  off,  washed  with  water, 
and  recrystallised  from  alcohol. 


THE  LINKING  OF  NITROGEN  TO  CARBON 


301 


3C6H6CHO  +  2NH3  =  C6H5CH<  +  3H20. 

XN  :  CH.CBH5 

M.P.  1 10°  ;  insoluble  in  water,  easily  soluble  in  alcohol.    (A.,  21,  130.) 

Reaction  CXLV. — Action  of  Nitrous  Acid  on  Certain  Ketones. — Forma- 
tion of  iso-nitroso  compounds.  Iso-nitroso  compounds  are  formed  by  the 
action  of  nitrous  acid  on  ketones  which  contain  the  — CH2.CO —  group. 

— CH2.CO—  +  HONO  ->  — C.CO— 

II  +  H20. 

NOH 

Preparation  281 . — Iso-nitroso-camphor. 

,C  :  NOH 

C8H14<  |  C10H15O2N.  181. 

\co. 

102  gms.  of  camphor  are  dissolved  in  550  c.cs.  of  pure  dry  ether  in  a 
litre  flask,  and  15-2  gms.  sodium  wire  added.  The  flask  is  well  cooled  in  a 
mixture  of  ice  and  salt,  and  78  gms.  of  isoamylnitrite  added  in  small 
portions,  the  flask  being  thoroughly  shaken  after  each  addition.  After 
standing  for  an  hour,  during  which  time  a  part  of  the  sodium  iso-nitroso 
camphor  separates,  the  contents  of  the  flask  are  slowly  poured  into  ice 
water.  An  ethereal  layer,  containing  borneol  and  unchanged  camphor, 
separates,  while  the  reddish-yellow  aqueous  layer  contains  the  sodium 
iso-nitroso  camphor.  The  aqueous  layer  is  separated,  extracted  twice 
with  ether,  and  any  dissolved  ether  removed  from  it  by  blowing  a  current 
of  air  through  it.  It  is  then  neutralised  with  dilute  acetic  acid  when  the 
iso-nitroso  camphor  is  precipitated.  The  precipitate  is  filtered  off, 
washed  with  water,  and  after  being  dried  in  a  steam  bath,  is  recrystallised 
from  a  mixture  of  petroleum  ether  and  benzene. 

/CH2  /C  :  NOH 

C8H14<  |     +  C5HnONO  ->  C8H14<  |  +  C5HnOH. 

xCO  xCO 

M.P.  152° — 154°  ;  long  prisms  ;  easily  soluble  in  ether,  alcohol,  alkali 
and  benzene  ;  difficultly  soluble  in  petroleum  ether.    (A.,  274,  73.) 


CHAPTER  XX 


THE  LINKING  OF  SULPHUR  TO  CARBON 

Sulphonic  Acids. 

Reaction  CXLVL— Action  of  Concentrated  Sulphuric  Acid  on  Hydro- 
carbons or  Substituted  Hydrocarbons. — When  cone,  sulphuric  acid 
acts  on  an  aromatic  hydrocarbon  or  substituted  hydrocarbon,  one  or 
more  of  the  H  atoms  in  the  nucleus  are  replaced  by  the  sulphonic  group 
(S02,OH). 

E.H  +  H2S04  — >  R.S02OH  +  H20. 

It  is  necessary  to  have  an  excess  of  sulphuric  acid  present  to  avoid 
dilution  of  the  acid,  which  would  occur  from  the  formation  of  water  in 
the  reaction. 

Some  sulphonic  acids,  e.g.,  benzene  and  toluene  sulphonic  acids,  may 
be  formed  at  ordinary  temperatures,  while  others  require  a  considerably 
higher  temperature.  In  some  cases  100%  H2S04  (monohydrate- — 
S03.H20)  is  necessary.  The  influence  of  temperature,  concentration  of 
acid,  time  of  reaction,  and  the  presence  of  other  substituted  groups  is 
very  marked,  and  different  isomers  are  formed  under  different  conditions. 

The  reaction  may  be  assisted  mechanically  by  mixing  with  kiesulgdhr, 
or  other  finely-divided  material,  and  catalytically  by  the  addition  of 
iodine  in  the  case  of  benzene,  and  of  boric  acid,  mercury  and  mercury 
salts  in  the  case  of  anthraquinone. 

The  sulphonic  group  is  strongly  acidic,  and  will  decompose  carbonates 
with  the  formation  of  stable  salts,  a  property  which  is  used  in  their 
separation.  The  presence  of  a  basic  group  in  the  nucleus  is  not  sufficient 
to  neutralise  its  acidity,  thus  sulphanilic  acid  is  distinctly  acid. 

Isolation  of  Sulphonic  Acids. — Sulphonic  acids  are  usually  isolated  in 
the  form  of  their  salts  in  order  to  get  rid  of  the  excess  of  sulphuric  acid 
used  in  the  reaction.  The  calcium  or  barium  salts  are  formed  where 
these  are  soluble  by  adding  lime  or  barium  carbonate,  and  the  excess 
sulphuric  acid  precipitated  as  CaS04  or  BaS04,  and  removed  by  filtration. 
The  filtrate  containing  the  salt  in  solution  may  then  be  concentrated  till 
the  salt  crystallises  out  or  it  may  be  evaporated  to  dryness.  The  sodium 
salt  may  be  obtained  from  the  sulphonation  mixture  by  diluting  and  adding 
a  saturated  solution  of  common  salt,  and  allowing  to  crystallise.  Isomers 
may  be  separated  by  the  fractional  crystallisation  of  their  salts  ;  it  is 
often  best,  however,  to  form  the  sulphonyl  chlorides  by  treatment  with 
PC15,  and  then  the  amides  by  the  action  of  ammonia  ("See  Preparation  289) ; 
after  fractional  crystallisation  of  the  amides  the  acids  are  set  free  by 
heating  under  pressure  with  hydrochloric  acid.    The  sulphonyl  chlorides, 

302 


THE  LINKING  OF  SULPHUR  TO  CARBON 


303 


and  the  sulphonamides  which  generally  crystallise  well  and  have  definite 
melting  points,  are  used  for  the  identification  of  sulphonic  acids. 

Tests  for  Complete  Sulphonation. — The  sulphonation  is  tested  by  the 
solubility  of  the  product  in  water  or  dilute  alkali.  Complete  solubility  is 
seldom  obtained  owing  to  the  formation  of  a  sulphone  by  condensation. 

R.SO3H  +  H.K  ->  R.S02.E  +  H20. 

The  sulphones  are  insoluble  in  water,  but  may  be  distinguished,  say, 
from  unchanged  naphthalene  by  extracting  and  taking  the  melting  point. 
The  following  factors  influence  the  formation  of  sulphones  :  concentration 
of  acid  (H2S04  or  S03),  temperature  of  sulphonation,  duration  of  sulphona- 
tion. Conditions  have  to  be  chosen  so  that  the  quantity  of  sulphone  is 
reduced  to  a  minimum. 

Apparatus  Used  in  Sulphonation. — The  most  convenient  type  of  appara- 
tus for  this  process  is  a  cast-iron  pot  with  a  good  mechanical  agitator, 
a  thermometer  pocket,  and  an  opening  for  reflux  condenser  (see  Fig.  36). 
It  is  of  the  utmost  importance  that  the  agitation  should  be  as  efficient  as 
possible.  Fig.  37  shows  a  convenient  apparatus  in  glass,  when  the  cast- 
iron  pot  is  not  procurable. 

Preparation  282. — Benzene  Sulphonic  Acid. 

C6H5.S03H.       C6H603S.  160. 

Method  I.  — 300  gms.  of  cone,  sulphuric  acid  (96%)  and  60  gms.  of 
benzene  are  placed  in  the  sulphonating  vessel  and  the  temperature  raised 
to  the  boiling  point  of  benzene,  80°  C,  the  agitation  being  maintained 
from  the  commencement  of  the  heating.  The  benzene  vapour  is  condensed 
and  returned  by  the  reflux.  The  heating  is  continued  for  8 — 10  hours, 
when  the  sulphonation  should  be  complete  (test).  Milk  of  lime  is  made  up 
in  a  basin  by  adding  1  part  of  lime  to  5  parts  of  hot  water,  and  stirring. 
The  sulphonation  is  cooled  down  and  poured  into  300  c.cs.  of  water. 

Isolation  of  Calcium  Salt. — The  milk  of  lime  is  now  carefully  added  with 
stirring  until  the  solution  is  just  neutral  (test  with  phenolphthalein 
paper).  It  is  then  boiled,  and  after  cooling  to  60°  C.  the  CaS04  is  filtered 
off  on  a  Buchner  funnel,  and  washed  with  a  little  hot  water. 

Isolation  of  Free  Acid. — To  the  filtrate  which  contains  the  Ca  salt  in 
solution,  dilute  sulphuric  acid  is  added  until  all  the  Ca  is  precipitated 
(test),  and  this  is  filtered  off  and  washed  with  a  little  hot  water.  The 
filtrate  is  then  evaporated  until  the  free  acid  crystallises  out. 

Isolation  of  Sodium  Salt. — If  the  acid  is  required  for  fusion  with  caustic 
soda,  the  sodium  salt  is  formed.  To  the  filtrate  containing  the  Ca  salt 
in  solution,  sodium  carbonate  is  added  until  no  more  CaC03  is  precipitated 
(test).  The  CaC03  is  filtered  off  and  washed,  and  the  filtrate  evaporated, 
leaving  the  Na  salt. 

C6H6  +  H2S04  ->  C6H5.S03H  +  H20. 

Yield. — 75 — 80%  theoretical.  Na  and  Ca  salts  white  powders, 
soluble  in  water  ;  used  in  preparation  of  phenol,  see  p.  204. 


304 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Method  II. — 15  gms.  pure  benzene,  90  gms.  of  sulphuric  acid  (D.  1-842) 
and  sufficient  washed  and  ignited  kieselgiihr  to  form  a  thin  paste  are 
shaken  together  and  allowed  to  stand  for  24  hours.  The  acid  is  isolated 
as  before. 

Yield. — Theoretical  (30  gms.).    (D.R.P.,  71556.) 
Preparation  283.— Naphthalene  /5-Sulphonic  Acid  (Na  salt). 

C10H8SO3.  208. 

120  gms.  of  cone,  sulphuric  acid  are  heated  to  160°  and  100  gms.  of  melted 
naphthalene  is  poured  in  from  a  basin,  good  agitation  being  maintained. 
When  all  the  naphthalene  is  added,  the  temperature  is  raised  to  170°  for 
3  hours,  and  then  to  180°  for  1  hour,  until  sulphonation  is  complete  (test). 
Excess  sulphuric  acid  is  removed  as  CaS04,  as  in  benzene  sulphonic  acid. 
The  filtrate  containing  the  calcium  salt  of  the  /?-acid,  as  well  as  some 
calcium  salt  of  the  a-acid  is  concentrated  until  a  sample,  on  cooling,  sets 
to  a  thick  mass.  It  is  allowed  to  crystallise  overnight  and  filtered,  the 
other  impurities  remaining  in  the  nitrate.  The  calcium  salt  is  then 
dissolved  in  hot  water,  and  the  sodium  salt  isolated  as  before. 


above  100°  ^N^NsOgH 
+  H2S04  >  ,3-acid. 


Yield. — 75%  theoretical  (130  gms.).    White  powder  ;  soluble  in  water  ; 
used  in  preparation  of  /5-naphthol.    (Rec,  1917,  20,  197.) 
Preparation  284. — rZ-Camphor-sulphonic  Acid  (Reychler's  Acid). 

C10H15O.SO3H.       C10H16O4S.  232. 

45  gms.  (1  mol.)  of  camphor  are  finely  powdered  and  added  to  a  well- 
stirred  mixture  containing  30  gms.  (1  mol.)  of  cone,  sulphuric  acid,  and 
60  gms.  of  acetic  anhydride.  The  camphor  dissolves  readily,  and  the 
solution  is  allowed  to  stand  for  2 — 3  days  until  no  more  (^-camphor 
sulphonic  acid  crystallises  out.  The  crystals  are  then  filtered  through 
asbestos  or  glass  wool,  washed  with  acetic  acid  until  colourless,  and 
recrystallised  from  acetic  acid  or  ethyl  acetate. 

C10H16O  +  H2S04  ->  C10H15O.SO2OH  +  H20. 

Yield. — 50%  theoretical  (27  gms.).    Large  prisms  ;    decompose  at 
193° ;  [a]D  =  +  21°.    (Bl.  [hi.],  19,  120  ;  J.  C.  S.,  81,  1442.) 
Preparation  285.— o-  and  ^-Toluene  Sulphonic  Acids. 

/CH3 

C6H4<  C7H803S.  172. 

130  gms.  pure  toluene  are  heated  with  450  gms.  cone,  sulphuric  acid 
in  a  cast-iron  pot  fitted  with  a  suitable  agitator  (see  Fig.  36).  The 


THE  LINKING  OF  SULPHUR  TO  CARBON 


305 


,  temperature  is  allowed  to  rise  to  100°,  a  crystal  of  iodine  being  added. 
The  sulphonation  is  complete  in  about  6  hours,  when  the  reaction  mixture 
is  transferred  to  a  large  basin,  diluted  with  water,  and  milk  of  lime  added 
gradually  to  neutralise  the  excess  acid.  The  calcium  sulphate  and  any 
ferric  hydroxide  present  are  removed  by  filtration  and  washed  with  hot 
f  water.  Sodium  carbonate  is  added  to  the  filtrate  until  just  alkaline  to 
phenolphthalein,  and  the  calcium  carbonate  filtered  off.  The  filtrate 
is  then  evaporated  almost  to  dryness,  when  the  sodium  salts  of  o-  and 
p-sulphonic  acids  separate  out. 

Yield. — 95%  theoretical  (340  gms.)  (total  o  and  <p). 
o-  Crystallises  with  2H20  ;  plates.    (Am.  Soc,  8,  176  ;  B.,  12,  1851.) 
p-  Crystallises  with  4H20  ;  plates  or  prisms  ;  M.P.  92°.    (Am.  Soc, 
v  10,  140.) 

Separation  of  o-  and  p-Toluene  Sulphonic  Acids. — The  mixture 
prepared  above  is  treated  gradually  with  an  equal  weight  of  finely 
pulverised  phosphorus  pentachloride.  When  the  reaction  is  complete, 
cold  water  is  added,  the  whole  being  surrounded  by  a  freezing  mixture. 
The  jo-sulphonyl  chloride  separates  as  a  solid,  and  is  filtered  off  and 
recrystallised  from  alcohol.  The  o-sulphonyl  chloride  is  an  oily  liquid, 
and  is  separated  from  the  filtrate  by  means  of  a  funnel. 

C6H4CH3S03Na  +  PC15  ->  C6H4CH3S02C1  +  POCl3  +  NaCl. 

jo-Sulphonyl  chloride.— Plates  ;  M.P.  69°  ;  B.P. 15  145°. 
o-Sulphonyl  chloride,— Oil.    (B.,  44,  2504.) 

Reaction  CXLVIX.  Action  of  Fuming  Sulphuric  Acid  (oleum)  on  Hydro- 
carbons or  Substituted  Hydrocarbons. — It  is  sometimes  difficult  to  intro- 
|  duce  a  sulphonic  group  by  means  of  cone,  sulphuric  acid,  and  it  is  then 
.necessary  to  use  fuming  acid  (i.e.,  acid  containing  up  to  70%  free  S03). 
The  same  factors  as  before  have  an  important  influence  on  the  reaction. 
Usually  a  high  temperature  is  necessary  where  more  than  one  S03H  has 
to  be  introduced.  In  some  cases  oleum  is  used  in  preference  to  sulphuric 
acid,  in  order  to  reduce  the  time  and  the  temperature  of  sulphonation. 

Estimation  of  S03  in  Oleum. — The  oleum  is  melted,  if  necessary,  by 
placing  the  bottle  in  hot  water  (caution  !),  and  a  quantity  is  dropped  into 
the  bottom  of  a  clean,  dry,  tared  test  tube  to  a  depth  of  about  1|  inches 
(8 — 10  gms.).  The  whole  is  weighed,  and  the  weight  of  oleum  obtained 
by  difference.  The  test  tube  is  now  heated  and  drawn  out  near  its  open 
end  and  sealed.  This  is  then  carefully  placed  in  a  graduated  litre  flask 
containing  about  500  c.cs.  of  water.  The  flask  is  securely  stoppered,  and 
the  test  tube  broken  by  shaking.  Shaking  is  continued  till  all  the  white 
fumes  disappear.  The  flask  is  then  allowed  to  cool,  and  its  contents 
|made  up  to  1  litre.  250  c.cs.  are  then  removed  and  titrated  with  normal 
caustic  soda  solution,  using  Methyl  Orange  as  an  indicator. 

If         W    =  weight  of  oleum 

n     =  c.cs.  of  N  NaOH  to  neutralise  W, 

0/  QA       4-9n  -  100W 
then%S03  =       .225W  . 

S.O.C.  X 


306  SYSTEMATIC  OKGANIC  CHEMISTEY 


The  percentage  of  S03  can  also  be  obtained  by  estimating  the  total 
H2S04  by  titration  given  by  the  oleum,  reckoned  as  H2S04.  The  %  excess 
of  H2S04  over  100,  when  multiplied  by  444,  gives  the  percentage  of  S03, 
e.g.,  if  total  H2S04  =  105%  of  the  oleum,  then  %  S03  =  5  X  4-44  =  22-2. 

The  results  obtained  are  a  little  high,  as  oleum  contains  a  small  per- 
centage of  S02.  This  may  be  estimated  by  titrating  250  c.cs.  with  N/10 
iodine  solution,  using  starch  as  indicator.  By  subtracting  this  result 
from  the  total  obtained  by  titration  with  NaOH,  the  true  percentage  of 
S03  can  be  calculated. 

Preparation  of  Oleum  of  a  given  Strength. 

1.  From  two  oleums  of  different  strength. 

oleum  =  a%  S03 
oleum  =  c%  S03 
oleum  =  b%  S03  required, 


then  x 


100  {a  -  h) 


o—  c 

where  x  =  quantity  of  c  to  be  added  to  100  gms. 
of  a  to  give  b. 
2.  From  oleum  and  cone,  sulphuric  acid. 

oleum  =  a%  S03 
cone,  sulphuric  acid  =  c%  H2SOi 

oleum  =  b%  required, 

then  x  -     100  6) 
then  x  -  fiT— 444^+5 

where  x  =  quantity  of  cone.  H2S04  to  be  added  to 
100  gms.  of  a  to  give  b, 

Pkepakation  286. — Nitrobenzene  m-sulphonic  Acid. 

SO~oH. 


N02<^       y  C6H505NS.  203. 

375  gms.  oleum  (25%  S03)  are  placed  in  a  cast-iron  sulphonation  pot 
and  heated  to  70°.  123  gms.  nitrobenzene  are  run  in  carefully.  Heat 
is  evolved  and  the  temperature  rises  up  to  100° — 110°,  and  must  not  be 
allowed  to  rise  higher.  The  inflow  of  nitro-benzene  must  be  slackened, 
or  external  cooling  applied,  if  necessary.  When  all  the  nitrobenzene 
has  been  added,  the  mixture  is  heated  to  110° — 115°,  until  sulphonation 
is  complete  (test).  The  odour  of  nitrobenzene  should  be  absent.  If 
the  sulphonation  is  not  complete  after  half  an  hour,  more  oleum  is 
added. 

The  mixture  is  allowed  to  cool,  and  is  then  poured  on  to  about  500  gms. 
ice,  with  good  stirring.  The  sulphonic  acid  passes  into  solution,  except 
some  sulphone  formed.  This  may  be  removed  by  filtration.  200  gms. 
common  salt  are  slowly  added  to  the  solution,  with  continuous  stirring, 
when  the  sodium  salt  crystallises  out,  and  after  standing  for  about 
10  hours,  is  filtered  off. 


THE  LINKING  OF  SULPHUR  TO  CARBON 


307 


Yield,— 90— 95%  theoretical  (200—214  gms.).  Plates;  chloride 
melts  at  60-5°  ;  used  for  preparation  of  metanilic  acid  (see  p.  353).  (A., 
120,  164.) 

This  process  is  used  in  the  sulphonation  of  j9-nitro-chlor-benzene, 
^-nitro-toluene,  o-nitro-chlor-benzene,  chlor-benzenes,  etc. 

Preparation  287. — Anthraquinone  -Sodium  Sulphonate  (Silver  Salt). 

CO 

X  303Na. 

C14H705SNa,  310. 

CO 

100  gms.  dry,  finely  divided  anthraquinone  are  added  cautiously  to 
150  gms.  oleum  containing  25%  S03,  with  continuous  stirring,  the  tempera- 
ture being  kept  under  30°.  The  temperature  is  then  raised  to  120°  during 
4  hours,  and  then  to  140°  during  a  further  2  hours,  using  an  oil  bath. 
The  vessel  must  be  kept  closed  to  prevent  loss  of  S03.  After  cooling,  the 
mixture  is  poured  into  3  litres  of  water  (caution  !)  and  the  unchanged 
anthraquinone  filtered  off  (25 — 40  gms.).  Chalk  is  added  to  the  filtrate 
until  completely  neutralised,  and  the  calcium  sulphate  filtered  off.  The 
calcium  salt  in  solution  is  then  precipitated  as  carbonate  by  adding 
dilute  sodium  carbonate  (test).  It  is  then  filtered  and  the  filtrate  evapo- 
rated down  to  about  400  c.cs.,  and  allowed  to  cool.  The  sodium  salt 
separates  out  after  standing  for  about  2  days.  It  is  then  filtered  and 
washed  with  a  little  water. 

Yield. — 40 — 60%  theoretical  (60 — 90  gms.).  Silvery  glistening  plates  ; 
soluble  in  water  ;  crystallises  with  1H20  ;  used  for  making  alizarin 
(see  p.  384).    (A.,  160,  131.) 

Preparation  288. — 1.8-Amino  Naphthol  3.6-Disulphonic  Acid  (H. 
acid)— Sodium  Salt. 

OH  NH, 

C10H9O7NS2.  319. 

Sulphonation. — 1024  gms.  of  24%  fuming  sulphuric  acid  (fuming  acid 
of  higher  strength  than  this  may  be  diluted  with  100%  sulphuric  acid), 
or  the  equivalent  of  fuming  acid  of  strength,  22 — 24%,  is  weighed  and 
introduced  into  a  sulphonation  pot.  The  acid  is  stirred  and  heat  applied 
until  the  temperature  reaches  100°  ;  128  gms.  of  naphthalene  are  added 
quickly  in  portions  at  a  time,  and  this  causes  a  considerable  rise  in 
temperature.  When  the  naphthalene  is  all  in,  the  temperature  is  raised 
to  165°,  at  which  it  is  maintained  for  8  hours,  with  slow  stirring.  During 
this  process  naphthalene  3.6.8-trisulphonic  acid  is  the  chief  product 
formed.  After  the  above  time  the  pot  is  allowed  to  cool  to  room 
temperature. 

titration, — At  room  temperature  the  sulphonation  mixture  should  be 
capable  of  being  stirred,  but  if  not,  cone,  sulphuric  acid  must  be  added 
until  the  contents  can  be  stirred.    The  pot  is  then  placed  in  a  bath,  which 


308  SYSTEMATIC  ORGANIC  CHEMISTRY 


can  be  filled  with  cold  water,  the  agitator  is  set  in  motion,  and  cone,  nitric 
acid  slowly  run  from  a  dropping-funnel  to  effect  nitration.  The  tempera- 
ture should  be  maintained  about  20°  during  nitration.  The  theoretical 
quantity  of  nitric  acid,  calculated  from  the  naphthalene  used,  is  necessary, 
and  acid  of  about  60%  is  preferable,  the  strength  being  ascertained  by 
use  of  a  hydrometer. 

After  the  nitric  acid  has  been  added,  the  mixture  is  allowed  to  stand 
at  25°  for  an  hour,  and  then  the  temperature  is  raised  to  50°  in  the  course 
of  the  next  hour.  After  this  time  it  is  poured  into  1,500  c.cs.  water  ; 
volumes  of  nitrous  fumes  are  given  off,  and  the  temperature  rises  con- 
siderably. During  this  process  l.nitro-3.6.8-naphthalene-trisulphonic 
acid  is  the  chief  product  formed. 

Reduction. — 256  gms.  of  iron  borings  are  weighed  and  about  10  gms.  of 
these  added  to  the  solution  of  nitro-sulphonic  acid  at  about  50°  ;  this 
causes  the  evolution  of  nitrous  fumes.  The  remaining  iron  is  added  in 
portions  at  such  a  rate  that  the  reduction  proceeds  briskly  ;  the  agitation 
should  be  vigorous  enough  to  keep  the  iron  swirling  round.  After  all 
the  iron  has  been  added,  agitation  is  continued  for  an  hour  ;  the  tempera- 
ture is  then  raised  to  50°,  150  gms.  of  common  salt  added,  and  the  agitation 
continued  for  an  hour  while  the  mixture  cools.  The  acid  sodium  salt  of 
naphthylamine-trisulphonic  acid  is  by  this  means  precipitated  ;  along 
with  any  unattached  iron  this  is  filtered  off  and  washed  with  10%  brine. 
The  contents  of  the  funnel  are  placed  in  a  vessel  and  boiled  up  with  water 
until  all  the  naphthylamine-sulphonic  acid  dissolves  ;  while  still  almost 
boiling  the  solution  is  again  filtered  to  separate  the  iron  residue.  The 
filtrate,  while  still  warm,  is  treated  with  15  gms.  common  salt  for  each 
100  c.cs.  volume  and  agitated  while  the  salt  dissolves ;  before  this  is 
complete,  separation  of  the  sulphonic  acid  begins.  The  mixture  is  after- 
wards cooled  to  15°,  and  the  purified  aminosulphonic  acid  (Na  salt) 
filtered  off.  The  precipitate  is  washed  on  the  funnel  with  100  c.cs.  of 
10%  brine,  pressed  in  a  screw  press  and  dried  at  100°.  When  dry  it  is 
ground  up,  and  a  sample  estimated  with  standard  nitrite  (see  p.  490) ;  it 
is  generally  of  75— 80%  purity. 

Caustic  Fusion. — This  operation  is  performed  in  a  small  autoclave,  for 
manipulation  of  which  see  p.  42.  85  gms.  caustic  soda  and  134  c.cs. 
water  are  placed  in  the  vessel  and  heat  applied  until  solution  takes  place  ; 
128  gms.  of  naphthylamine-trisulphonic  acid  (70%- — 80%)  are  then  added, 
and  the  lid  of  the  autoclave  bolted  on.  The  mixture  is  gradually  heated 
up  to  180°  and  maintained  at  this  point  for  5  hours,  the  pressure  being 
about  100  lbs.  After  cooling,  the  autoclave  is  opened,  allowing  any 
residual  pressure  to  escape  gradually — a  certain  amount  of  ammonia  is 
always  present.  The  reaction  product  is  introduced  into  a  large  beaker 
or  stoneware  jar,  diluted  with  750  c.cs.  water,  and  acidified  with  cone, 
hydrochloric,  or  50%  sulphuric  acid  ;  volumes  of  sulphur  dioxide  from  the 
decomposition  of  the  sodium  sulphite  are  given  off.  When  testing  for 
acidity,  a  small  sample  should  be  withdrawn  and  boiled  to  expel  sulphur 
dioxide,  prior  to  testing  with  Congo  paper.  The  aminonaphthol-disul- 
phonic  acid,  which  is  formed  in  this  reaction,  being  only  very  sparingly 


THE  LINKING  OF  SULPHUR  TO  CARBON 


309 


soluble  in  solutions  of  sodium  chloride  or  sulphate,  is  practically  all 
precipitated  as  the  mono-sodium  salt  on  acidification.  After  acidification 
the  mixture  is  cooled  to  room  temperature  and  allowed  to  stand  for  1  hour. 
The  precipitate  is  then  filtered  off,  washed  with  100  c.cs.  of  10%  brine, 
pressed,  and  dried  at  100°. 


SOJI  NIL 


NO, 


SO,H 


S03H 
OH  NH 


SO,H 


SO,Hl 


SO»H 


SO,H 


lSO,H. 


Sodium 
(B.,  27, 


Yield. — 50  gms.  of  80—85%  purity  (see  estimation,  p.  490). 
salt  soluble  in  water  and  crystallises  with  1 JH20  ;  fine  needles. 
2148  ;  D.R.P.,  69722.) 

Reaction  CXLVIII.  Action  of  Cfoloro-sulplionic  Acid  (C1.S03H)  on 
Hydrocarbons  or  Substituted  Hydrocarbons. — Ohloro-sulphonic  acid  (see 
p.  507)  is  used  for  sulphonating  in  special  cases.  In  this  sulphonation 
HC1  is  evolved. 


E.H  +  Cl.SO„H 


HC1. 


The  chief  advantage  in  the  use  of  this  acid  is  its  selective  property, 
whereby  certain  sulphonic  acids  are  formed,  which  could  not  be  formed 
by  direct  sulphonation  with  sulphuric  acid  or  oleum,  or  which  might  be 
formed  only  in  presence  of  other  isomers,  the  separation  of  which  might 
be  difficult.  For  example,  naphthalene  sulphonated  with  oleum  at  the 
ordinary  temperature  gives  a  mixture  of  1-5-  and  1-6-disulphonic  acids, 
while  chloro-sulphonic  acid  yields  only  the  1-5-acid.  Similarly,  with 
toluene,  chiefly  the  ortho  acid  is  formed.  With  excess  of  chloro-sulphonic 
acid  a  sulphonyl  chloride  is  formed,  except  in  the  case  of  phenols  or 
naphthols,  which  give  the  free  sulphonic  acid. 

E.H  ~>  K.S02OH  ->  R.S02C1. 

When  chlorosulphonic  acid  reacts  with  amides,  acid  chlorides  are 
formed,  while  amines  yield  sulphaminic  acids. 

SO3HCI  +  3C6H5NH2  ->  C6H5NH.S03H.C6H5NH2  +  C6H5NH2.HCL 

When  the  sulphonic  acid  produced  by  the  interaction  of  chloro-sulphonic 
acid  has  to  be  nitrated  afterwards,  it  must  be  isolated  previous  to  nitration, 
otherwise  the  chlorine  liberated  may  form  chlor-derivatives. 

Preparation  289. — Saccharin  (^-Benzoyl  sulphonimide). 


183. 


1.  Toluene  o -sulphonyl  chloride. — 100  gms.  pure  toluene  are  slowly  run 


310  SYSTEMATIC  ORGANIC  CHEMISTEY 


into  500  gms.  of  chloro-sulphonic  acid  cooled  to  0°  in  a  pot  fitted  with 
good  mechanical  agitation,  the  temperature  during  the  addition  being 
kept  below  5°.  When  all  the  toluene  has  been  added  stirring  is  continued 
for  about  12  hours  at  the  same  temperature.  The  mass  is  then  poured 
on  to  ice,  when  an  oily  layer  separates.  The  liquid  ortho-sulphonyl 
chloride,  which  usually  contains  some  of  the  solid  para-compound,  is  then 
separated  and,  after  further  treatment  with  ice  and  salt,  is  filtered  and 
the  ortho  compound  separated  from  the  salt  solution  in  a  funnel. 

The  pot  in  which  the  sulphonation  is  carried  out  should  have  an  exit 
tube  for  the  escape  of  HC1,  which  may  be  absorbed  in  fuming  sulphuric 
acid  with  the  formation  of  more  chlorosulphonic  acid. 

,CH3 

C6H6CH3  — >  C6H4<( 

\S02C1. 

Yield.— Ortho  85%  theoretical  (110  gms.).    (E.P.,  25273,  1894.) 

2.  Toluene  o-sulphonamide. — The  o-sulphonyl  chloride  is  gradually 
added  to  an  equal  quantity  of  20%  ammonia  solution,  which  is  cooled  in  a 
freezing  mixture.  When  all  has  been  added,  the  reaction  is  completed 
by  removing  the  freezing  mixture  and  gently  heating.  The  sulphon- 
amide  is  then  filtered  off  and  dissolved  in  N.  caustic  soda  solution,  filtered, 
and  reprecipitated  by  adding  sufficient  hydrochloric  or  sulphuric  acid  to 
precipitate  75%  of  the  amide  in  solution.  The  precipitate  is  redissolved 
by  heating,  and  almost  pure  o-sulphonamide  crystallises  out  on  cooling 
(M.P.  133°— 134°). 

/CHo  /CHo 


C6H4\  ~~ >  C6H4/ 

XS02C1  \S02NH2. 


(E.P.,  22726,  1894  ;  3930,  1895  ;  848,  1903  ;  D.R.P.,  133919.) 

3.  Saccharin. — One  equivalent  of  the  o-sulphonamide  (171  gms.)  is 
dissolved  in  one  equivalent  of  caustic  soda  (40  gms.)  and  2,565  gms.  of 
water.  This  is  heated  to  40° — 50°,  and  256  gms.  of  solid  potassium 
permanganate  are  slowly  added  with  stirring.  When  all  the  permanganate 
has  been  added  and  the  colour  has  almost  disappeared,  a  little  NaHS  is 
added  to  decolorise,  and  the  precipitated  manganese  compound  filtered 
off  and  washed  with  water  until  acid  added  to  the  filtrate  gives  no  precipi- 
tate of  saccharin.  The  combined  nitrate  and  washings  is  then  cooled 
down  to  ordinary  temperature  and  neutralised  with  hydrochloric  acid, 
using  methyl  orange  as  indicator.  This  treatment  precipitates  unchanged 
o  sulphonamide,  which  is  filtered  off.  Hydrochloric  acid  is  then  added 
to  the  filtrate,  and  the  precipitated  saccharin  filtered  off,  washed  with 
water,  and  dried  at  40°. 

/CH3  .CO  x 

C6H/  ->  C6H4<  \nH. 

\S02NH2  \SO/ 

White  crystalline  powder  ;  M,P.  220° ;  soluble  in  hot  water  and  in 


THE  LINKING  OF  SULPHUR  TO  CARBON  311 


alcohol,  and  in  alkalis  or  alkali  carbonates  with  formation  of  salts.  (E.P., 
3563,  1903.) 

Reaction  CXLIX.  Intramolecular  Rearrangement  of  Aromatic  Amine 
Sulphates. — When  sulphuric  acid  is  added  to  an  amine  a  sulphate  is  usually 
formed.  If  the  sulphate  is  heated  either  alone  (baking  process)  or  with 
excess  of  cone,  sulphuric  acid,  a  rearrangement  takes  place,  the  sulphonic 
group  entering  the  ^-position  to  the  basic  group. 

")nh2  — >  /"  ~\nh2.h2so4  ->  so3h/     \nh2  -f  H20. 

Sulphonic  acids  can  be  made  by  the  baking  process,  which  are  difficult 
to  make  in  the  ordinary  way,  e.g., 

By  ordinary  process  NH2<^       ^> — ^>NH2  (a) 

£OzK  S03H 
By  baking  process      ->    NH2^      ^>-^      ^>NH2  (b) 

S03H  SO^H 

(a)  yields  cotton  dyestuffs,  while  (b)  yields  wool  dyestuffs. 
Another  advantage  of  the  baking  process  is  that  much  less  sulphuric 
acid  is  required. 

Preparation  290. — Sulphanilic  Acid  (l.Amino-4.benzene-sulphonic 
acid). 

NH2<^      ^S03H.       C6H703NS.  173. 

Method  I. — 20  gms.  of  aniline  are  gradually  added  to  65  gms.  of  cone, 
sulphuric  acid  placed  in  a  round-bottomed  flask.  Much  heat  is  developed, 
and  the  contents  of  the  flask  should  be  cooled  when  the  aniline  is  being 
added.  The  flask  which  contains  aniline  sulphate  and  excess  cone,  sulphuric 
acid  is  now  heated  on  an  oil  or  paraffin  bath  to  185°  for  about  5  hours. 
When  a  test  portion,  treated  with  dilute  caustic  soda  solution,  liberates 
no  free  aniline,  the  sulphonation  is  complete.  The  contents  of  the  flask, 
after  cooling,  are  poured  into  cold  water,  when  the  sulphanilic  acid 
separates,  usually  as  discoloured  crystals.  These  are  filtered  off  and 
recrystalhsed  from  water,  adding  a  little  animal  charcoal,  if  necessary. 
A  further  crop  can  be  obtained  from  the  mother  liquor. 

/~  -)NH2  ->   S03H<^  ~\NH2. 

Yield. — 55%  theoretical  (20  gms.). 

Method  II.  (baking  process). — 93  gms.  of  aniline  are  placed  in  a  basin 
and  105  gms.  of  cone,  sulphuric  acid  gradually  added  in  a  stream,  with 
good  agitation.  The  hot  paste  is  then  spread  on  a  lead  tray  and  placed 
in  an  air  oven  at  190° — 200°  for  8  hours.  The  cake  is  now  ground 
up  and  boiled  for  some  time  with  water  to  which  some  caustic  soda 
has  been  added  till  alkaline,  to  remove  the  unchanged  aniline  present 
(about  3%).    It  is  then  filtered  through  a  cotton  filter,  and  the  acid  is 


312  SYSTEMATIC  OKGANIC  CHEMISTRY 


obtained  by  adding  sulphuric  acid  to  the  filtrate  until  acid  to  Congo 
paper.  If  the  acid  is  discoloured  it  may  be  boiled  up  with  animal  charcoal, 
filtered,  and  allowed  to  crystallise. 

/~  ~^>NH2  +  H2S04  ->   /"    \NH2.H2S04  -> 

NH2^'      ^>$03H  +  H20. 

Yield. — 90%  theoretical  (155  gms.).  Rhombic  crystals ;  does  not 
melt ;  forms  two  hydrates  :  -2H20  when  crystallised  below  20°  ;  -1H20 
when  crystallised  between  20° — 44°  ;  important  intermediate  for  dye- 
stuffs.    (A.,  100,  163 ;  Z.  a.  (1896),  9,  685.) 

Preparation  291, — Naphthionic  Acid  (1-Naphthylamine  4-sulphonic 
acid). 


/        >S03H       C10H9O3NS.  223. 


The  process  is  similar  to  that  used  for  sulphanilic  acid.  70  gms.  of 
a-naphthylamine  and  50  gms.  of  cone,  sulphuric  acid  are  used.  Before 
the  paste  is  spread  on  the  tray  it  is  mixed  with  about  3  gms.  of  oxalic 
acid.  It  is  then  placed  in  the  oven  and  heated,  as  before.  When 
the  mass  has  been  cooled  and  powdered,  it  is  boiled  up  with  water  and 
neutralised  with  milk  of  lime  (test)  and  filtered.  The  acid  is  obtained 
by  acidifying  the  filtrate  with  hydrochloric  acid. 

Yield.— 80— 85%  theoretical  (88—94  gms.).  Crystallises  with  1H20 ; 
used  largely  in  preparation  of  azo  dyestuffs.  (B.,  13,  1948  ;  19,  578  ; 
Z.  a.  (1896),  9,  685.) 

Reaction  CL.  Action  of  Sulphites  and  Bisulphites  on  Substituted  Hydro- 
carbons.— (a)  Metallic  sulphites  and  bisulphites  are  used  in  certain  cases 
for  introducing  the  S03H  group,  and  especially  to  replace  halogens  where 
the  halogen  is  in  the  nucleus,  and  ortho  to  a  N02,  S03H  or  CHO  group. 

_N02  _N02 
N02<^  +  Na2S03  ->  N02<^      ^>S03Na  +  NaCl. 

(6)  In  some  cases  reduction  takes  place  simultaneously  with  sulphona- 
tion,  e.g.,  m-dinitrobenzene  gives  m-nitranihne  sulphonic  acid,  and  nitro- 
benzene diazonium  chloride  gives  ^-nitrophenylhydrazine  sulphonic 
acid. 

(c)  The  same  reagents  are  used  for  the  formation  of  alkyl  sulphonic 
acids  by  interaction  with  alkyl  halides. 

C2H5I  +  Na2S03  ->  C2H5S03Na  +  Nal. 

Halogens  in  the  side  chain  of  aromatic  compounds  also  undergo  this 
reaction. 

(d)  With  certain  olefinic  compounds,  additive  compounds  are  formed. 

E.CH  =  CH.COOH  +  K2S03->  K.CH2CH(COOH)S03K. 


THE  LINKING  OF  SULPHUR  TO  CARBON 


313 


Preparation  292. — Phenylhydrazine  ^  Sulphonic  Acid. 

NH.NH, 


C6H803N2S.  188. 


0,H. 


51  gms.  sulphanilic  acid  (100%)  are  dissolved  in  200  c.cs.  water  and 
16  gms.  caustic  soda.  Any  aniline  which  may  be  present  is  boiled  off. 
The  solution  is  filtered  and  cooled,  and  35  gms.  cone,  sulphuric  acid 
are  added.  The  whole  is  then  cooled  to  12°  (external  cooling),  and 
treated  with  a  solution  of  21  gms.  sodium  nitrite  in  50  c.cs.  water  during 
^  hour  with  continuous  stirring  until  a  distinct  and  permanent  reaction 
is  given  with  starch  iodide  paper.  The  diazo  sulphanilic  acid  separates 
out  as  fine  crystals,  which  are  filtered  off,  but  not  dried. 

The  moist  diazo  acid  is  then  added  to  a  mixture  of  130  gms.  bisulphite 
solution  (containing  25%  S02)  and  enough  35%  caustic  soda  solution 
to  give  a  distinct  alkaline  reaction  with  phenolphthalein  to  the  sulphite 
solution  (25 — 45  gms.  may  be  necessary).  The  temperature  of  the 
mixture  is  kept  below  50°  by  placing  the  vessel  in  ice-water  and  stirring. 
The  diazo  sulphanilic  acid  is  at  once  converted  into  the  sulpho-phenyl 
azo  sulphonic  acid,  which  is  allowed  to  stand  for  an  hour.  The  yellow 
solution  is  then  heated  to  boiling,  and  then  about  250  gms.  cone,  hydro- 
chloric acid  are  added  until  reaction  is  strongly  acid.  This  reaction  should 
be  performed  in  a  fume  cupboard.  The  reduction  takes  place  by  means 
of  the  S02  produced.  If  the  solution  does  not  become  decolorised  a 
little  zinc  dust  may  be  added.  The  phenylhydrazine  sulphonic  acid  crys- 
tallises out  on  standing.    It  is  filtered  and  washed  with  a  little  water. 


N  =  N- 


N  =  N.SO,H         NH.NH.SO,H  NH.NH 


S03H  S03  — 

Yield. — 90%  theoretical  (47  gms.).  Acid  ;  crystallises  with  |H20  ; 
soluble  in  hot  water  ;  alkali  salts  readily  soluble  ;  important  intermediate 
for  dyes.    (B.,  18,  3172  ;  A.,  190,  69.) 

Preparation  293.— m-Phenylene  Diamine  Sulphonic  Acid  (1.2.4). 

NH2 

S03H<^       ^>NH2.       C6H803N2S.  188. 

101  gms.  dinitro  chlor-benzene  are  dissolved  in  250  c.cs.  of  methylated 
spirits.  To  this  is  added  40  gms.  S02,  in  the  form  of  a  cone,  solution  of 
sodium  sulphite — about  160  gms.  NaHS03,  containing  25%  S02  mixed 
with  50  gms.  40%  NaOH  until  alkaline  to  phenolphthalein.  The  sulphite 
may  separate  out,  even  when  mixture  is  hot,  but  this  is  of  no  consequence. 
The  mixture  is  heated  on  the  water  bath  to  boiling  for  5  hours  with  good 


314  SYSTEMATIC  ORGANIC  CHEMISTRY 


stirring.  The  product  is  then  cooled,  and  the  sodium  salt  of  the  dinitro- 
benzene  sulpho  acid  separates  in  glistening,  yellow  leaflets. 

The  sodium  salt  is  then  reduced,  as  in  the  preparation  of  m-phenylene 
diamine  (see  p  352.). 

The  solution  of  the  diamine  sulphonic  acid  is  evaporated  down  to  about 
200  c.cs.  and  50  gms.  common  salt  added.  It  is  then  just  acidified  with 
HC1  (Congo  paper  should  be  turned  only  faint  violet),  and  the  free  acid 
crystallises  out.    It  is  filtered  and  washed  with  very  little  water. 

NQ2  NQ2  NH2 

Cl<^      ^>N02  ->  S03H<^      ^>N02  ->  S03H<^  ^>NH2. 

Yield. — 65%  theoretical  (61  gms.).  Dimorphous  ;  a-form,  monoclinic 
plates  ;  /?-form,  triclinic  prisms  ;  calcium  and  barium  salts  easily  soluble 
in  water.    (A.,  205,  104.) 

Preparation  294. — Dinitro-Stilbene-Disulphonic  Acid  (Na  salt). 

_S03H  SQ3H 
N02<^^^)CH  =  CH<(  ^>N02.       C14H10O10N2S2.  430. 

100  gms.  ^-nitrotoluene  are  sulphonated,  as  described  for  nitrobenzene 
(p.  3C6),  and  the  sodium  salt  separated.  It  is  dissolved  in  500  c.cs.  water 
at  60°  with  the  addition  of  sodium  carbonate  (about  50  gms.).  The 
solution  is  filtered  from  iron  oxide  and  made  up  to  2  litres  at  50°.  160  gms. 
of  35%  caustic  soda  solution  are  added  during  \  hour.  No  sodium 
salt  should  separate  out.  A  mixture  of  1,700  gms.  sodium  hypochlorite 
solution,  containing  about  5%  NaOCl  and  300  gms.  of  35%  caustic  soda 
solution  is  allowed  to  drop  in  during  10  hours.  The  temperature  must 
not  exceed  56°,  otherwise  yellow  dyestuffs  are  formed.  The  mixture  is 
allowed  to  stand  at  55°  for  24  hours.  Free  chlorine  should  be  present 
during  the  whole  period  (test  with  starch  potassium  iodide  paper).  It 
is  then  cooled  to  ordinary  temperature  and  400  gms.  salt  added. 
After  standing  for  a  day  the  yellow  crystalline  sodium  salt  of  the  acid  is 
precipitated,  and  is  filtered  off  and  washed  with  brine. 

SO3H  _  S03H  SQ3H 

CH3<^       \n<32  — >  CH3<^      ^>N02  ->  N02/       ^CH  =  CH<^  ^>N0 

Yield. — About  40%  theoretical  (60  gms.).    Used  for  preparation  of 
diamido-stilbene-disulphonic  acid  and  stilbene  dyestuffs.    (B.,  30,  3100.) 
Preparation  295. — 1-2*4  Amino-naphthol  Sulphonic  Acid. 

NH2 

C10H9O4NS.  239. 


100  gms.  of  ^-naphthol  are  converted  into  the  corresponding  nitroso- 
naphthol  (see  preparation,  p.  277).  The  moist  nitroso-naphthol  is  stirred 
up  with  a  little  water  and  cooled  to  5°  C.  with  ice.    To  the  paste  260  gms. 


THE  LINKING  OF  SULPHUR  TO  CARBON  315 


sodium  bisulphite  solution,  containing  25%  S02,  is  quickly  added.  The 
nitroso-naphthol  goes  into  solution  after  a  few  minutes ;  a  small  quantity 
of  dilute  caustic  soda  can  be  cautiously  added,  if  necessary.  The  solution 
is  filtered  to  remove  resinous  matter.  The  filtered  solution  is  treated  at 
25°  with  100  gms.  cone,  sulphuric  acid,  which  has  been  diluted  with 
200  gms.  of  water.  The  solution  should  then  give  a  strongly  acid  reaction. 
It  is  allowed  to  stand  for  1  hour,  and  is  then  warmed  to  50°  and  left  over- 
night— it  solidifies  to  a  solid  cake.  It  is  filtered  off  and  washed  well  with 
water. 

OH 

N.S03Na 
OH  /\/\0H 


Dioxine."  SO,H. 


Yield. — 90%  theoretical  (149  gms.).  Almost  insoluble  in  cold  water, 
sparingly  soluble  in  hot ;  sodium  salt  sparingly  soluble  in  hot  water. 
(B.,  27,  23.) 

Preparation  296. — Phenyl-Sulpho-Propionic  Acid  (K  salt)  (2-Sulphonic 
acid-3-phenyl-propan  acid). 

C6H5.CH2CH.(COOH)(S03K).       C9H905SK.  268. 

15  gms.  (1  mol.)  of  cinnamic  acid  and  13  gms.  (1  mol.)  of  normal 
potassium  sulphite  are  refluxed  with  280  c.cs.  of  water  for  12  hours,  then 
allowed  to  cool,  and  acidified  with  acetic  acid.  A  crystalline  precipitate 
of  phenyl  sulpho  propionic  acid  separates,  which  is  filtered  off  and  recrystal- 
lised  from  water.  A  further  yield  may  be  obtained  by  evaporating  the 
filtrate  to  dryness,  extracting  the  potassium  acetate  with  hot  alcohol, 
and  crystallising  the  residue  of  phenyl- sulpho- propionic  acid  from  water. 

C6H5CH  :  CH.COOH  +  K2S03  +  CH3.COOH  -> 
C6H5CH2.CH(COOH)(S03K)  +  CH3COOK. 

Needles  ;   melts  and  decomposes  on  heating  ;   soluble  in  hot  water 
(A.,  154,  63.) 
Preparation  297. — Ethyl  Sulphonic  Acid  (Ba  salt). 

CH3.CH2.S03H.       C2H603S.  110. 

20  gms.  (2  mols.)  of  ethyl  iodide  are  boiled  under  reflux  with  a  solution 
of  20  gms.  (excess)  of  crystallised  ammonium  sulphite  in  40  c.cs.  of  water 
until  all  goes  into  solution  (6  hours).  100  c.cs.  of  water  are  added,  and 
the  solution  boiled  with  30  gms.  (excess)  of  lead  oxide  until  all  ammonia 
is  expelled.  The  lead  salt  of  ethylsulphonic  acid  and  lead  iodide  are 
formed  ;  the  latter  is  removed  by  nitration  after  the  solution  cools. 
Sulphuretted  hydrogen  is  passed  into  the  filtrate  until  no  more  lead 
sulphide — from  the  decomposition  of  the  lead  salt  of  ethylsulphonic 
acid — is  formed.  Lead  sulphide  is  filtered  off,  and  the  filtrate  neutralised 
by  the  addition  of  excess  (20  gms.)  of  barium  carbonate.  After  filtration, 
the  filtrate  containing  barium  ethyl  sulphonate  is  evaporated. 


316 


2C2H5I 


SYSTEMATIC  ORGANIC  CHEMISTRY 

2NH4OH  +  2NHJ. 
->(CaH5S020)3Ba. 


2(NH4)2S03  +  2H20  ->  2C2H5S02OH 
PbO  H2S 
2C9H5S02OH  >  (C2H5SOoO)2Pb  >  2C2H5S02OH 


Yield.— 90%  theoretical  (22  gms.).    (A.,  168,  146.) 
The  free  acid  is  stable  and  forms  a  deliquescent  crystalline  mass  (B.,  15, 
445). 

Reaction  CLL   Action  of  Poly-sulphates  on  Certain  Hydrocarbons. — The 

S03H  group  may  be  introduced  in  certain  cases. 


C6H6  +  KH3(S04)3 
Na2S207  may  also  be  used. 


C«H,SO,H  +  KHSO, 


SO,H 


HftO. 


.H. 


+  Na2S20, 


In  the  anthraquinone  series  NaHS04  may  be  used. 
Prepaeation  298— Benzene  Sulphonic  Acid. 

20  gms.  of  benzene  and  50  gms.  potassium  polysulphate  are  heated  under 
a  reflux  until  all  the  benzene  has  dissolved.  The  cold  product  is  dissolved 
in  water  and  neutralised  with  milk  of  lime  and  isolated  as  before. 

C6H6  +  KH3(S04)2  ->  C6H5S03H  +  KHS04  +  H20. 

(D.R.P.,  113784.) 
Reactions  of  the  Sulphonic  Group. 

E.OH 

E.COOH       t  E.H 


E.CN 


E.SOJE 


E.S09C1 


E.C1 


K.NO, 


HC1 


(a) 

(&) 
(a) 
(*) 


E.OH. 


->  E.H. 


E.SO3H  +  NaOH 

E.S03H  +  H20 

pressure 

E.S03H  +  H+  +  OH'  ->  E.H 
NaHS03 

R.BO,Il  4-  XII,  — > 


R.NH,. 


pressure 


E.S03H  +  NaNH2 
E.S03H  +  HNO3 
E.S03H  +  CI 


(a) 

(b)  E.S03H  +  PCI, 
E.SO  JI  +  PCI, 


E.S03Na 
E.SO,Na 


NaCN 
NaCOOH 


E.N02. 

E.C1  (goes  readily  if  S03H  in 
a -position). 

E.CL 
E.S02C1. 
E.CN. 
EtC00H, 


:! 


CHAPTER  XXI 

THE  LINKING  OF  SULPHUR  TO  CARBON  (continued) 

Reaction  CLII.  Action  of  Sulphur  and  Sodium  Sulphide  on  Aromatic 
Bases. — Aromatic  amines  usually  react  with  sulphur  when  heated  some- 
times in  presence  of  sodium  sulphide  to  give  compounds  of  complex 
*  structure,  two  nuclei  joining  together  through  the  $-atom.  Several 
compounds  are  usually  formed  in  the  reaction,  e.g.,  ^-toluidine  gives 
'four  different  products  when  fused  with  sulphur.  The  final  products 
are  dyestuffs,  some  of  unknown  constitution,  and  are  known  as  sulphur 
or  sulphide  dyestuffs. 

The  formulae  show  the  compounds  obtained  from  j9-toluidine. 

CHq  CHo  CHo  CHo 


-S- 


Thio-^-tohiidine.  N=  =C  — \_  _/NH2. 

Dehydro-thio-j9-tolujdine. 


Bis-dehydro-thio-p-toluidine  or  Primuline  base. 

The  dyestuffs  produced  are  of  various  shades ;  generally  speaking, 
diphenylamines  give  blue  and  black  dyes,  toluidines  yellow  and  brown, 
and  diamines  red  dyes. 

For  dyestuff  preparations,  see  section  on  Dyes. 

Preparation  299. — Thiodiphenylamine  (o-Diphenylene-sulpho-imide) . 

I ...  /NHv 

C6H4<        >C6H4.       C12H9NS.  199. 

22  gms.  of  diphenylamine,  8-2  gms.  of  sulphur,  and  3-2  gms.  of  anhydrous 
aluminium  chloride  are  melted  together.  The  reaction  sets  in  at  140° — 
150°  with  rapid  evolution  of  sulphuretted  hydrogen ;  by  lowering  the 
temperature  a  few  degrees  the  reaction  can  be  slackened.    When  it  has 

317 


318  SYSTEMATIC  ORGANIC  CHEMISTRY 


moderated,  the  temperature  is  raised  to  160°  for  a  time.  The  melt, 
when  cool,  is  ground  up  and  extracted,  first  with  water  and  then  with 
dilute  alcohol.  The  residue  consists  of  almost  pure  thiodiphenylamine. 
It  can  be  recrystallised  from  alcohol. 

C6H5— NH-C6H5  +  2S  ->  C6H4/       \C6H4  +  H2S. 

Yield.— 93%  theoretical  (23-5  gms.).    Yellowish  leaflets  ;  M.P.  180°. 
(D.R.P.,  237771.) 
Preparation  300.— Dehydro-thiotoluidine. 

CH3<^  =  C— ( _    ")NH2.       C14H12N2S.  240. 

107  gms.  jo-toluidine  are  heated  with  70  gms.  powdered  sulphur  (not 
flowers  of  sulphur)  and  1  gm.  sodium  carbonate  (to  remove  acidic  sub- 
stances in  the  sulphur)  to  180°  in  a  sulphonating  pot  fitted  with  a  good 
agitator  and  reflux  condenser.  The  H2S  which  is  evolved  is  absorbed  by  a 
tower  filled  with  lumps  of  moist  caustic  soda.  The  temperature  is  raised 
to  220°  after  about  8  hours,  by  which  time  the  evolution  of  H2S  slackens, 
and  kept  at  220°  for  5  hours.  The  evolution  of  H2S  now  practically 
ceases,  and  the  melt  is  then  poured  on  to  a  tray  to  solidify. 

The  yellow  crust  is  then  finely  ground  and  extracted  with  95%  alcohol. 
This  dissolves  the  toluidine,  thiotoluidine,  and  the  dehydro-thiotoluidine, 
leaving  the  insoluble  primuline  base.  The  extract  is  evaporated  to 
dryness  and  heated  to  250°,  which  removes  the  toluidine  and  part  of  the 
thiotoluidine.  The  mixture  is  then  sulphonated  with  25%  oleum  and 
poured  on  to  ice,  filtered,  and  well  washed  with  water  until  the  washings 
give  only  a  faint  acid  reaction.  The  toluidine  and  thiotoluidine  sulphonic 
acids  pass  into  solution.  The  residue  is  dissolved  in  50  gms.  of  20% 
ammonia  solution  and  800  c.cs.  water,  and  heated  to  80°,  other  400  c.cs. 
of  water  being  then  added.  The  solution  is  filtered  hot,  if  necessary,  and 
the  ammonium  salt  of  dehydro-thiotoluidine  sulphonic  acid  separates  out 
in  the  course  of  2  days.  Primuline  can  be  obtained  from  the  mother 
liquor  by  saturating  with  15%  common  salt  at  the  boiling  point. 

Yield. — Ammonium  salt,  25  gms.  ;  primuline,  80  gms.  Base — needles 
(from  alcohol)  ;  M.P.  190°— 191°  ;  B.P.  434°  ;  primuline  (see  p.  382). 
(B.,  22,  333  ;  22,  424  ;  25,  1084.) 

Reaction  CLXII.  Action  of  Sulphur  Dioxide  on  Aromatic  Hydrocarbons 
in  presence  of  Aluminium  Chloride  or  Mercuric  Chloride.  (A.  Ch.  [6],  14, 
443.) 

A1C13 

C6H6  +S02  >C6H5S02H. 

The  sulphinic  acids  are  unstable  liquids  passing  readily  into  sulphonic 
acids  on  oxidation  with  alkaline  permanganate. 


THE  LINKING  OF  SULPHUR  TO  CARBON  319 


Sulphinates  may  also  be  formed  by  : — 

1.  Action  of  S02  on  zinc  alkyls. 

(C2H5)2Zn  +  2S02  ->  (C2H5S02)2Zn. 

2.  Action  of  zinc  on  sulphonyl  chlorides. 

2C2H5S02C1  +  2Zn  ->  (C2H5S02)2Zn  +  ZnCl2. 

Reaction  CLIV.  Action  o£  Sulphur  Dioxide  on  a  Diazonium  Compound 
in  presence  of  Finely  Divided  Copper.    (Gattermann  B.,  32,  1136.) 

Cu 

R.N2C1  +  S02  +  H20  ->  R.S02H  +  N2  +  HC1. 

This  method  gives  good  yields,  and  is  specially  useful  where  isomers 
are  formed  by  ordinary  or  direct  sulphonation.  For  example,  the 
o-toluene  sulphonic  acid  is  prepared  from  o-toluidine,  and  so  on. 

Preparation  301. — Benzene  Sulphinic  Acid. 

C6H5S02H.       C6H602S.  142. 

About  6  gms.  of  aniline  are  dissolved  in  dilute  sulphuric  acid  and 
the  solution  diazotised  in  the  usual  manner.  Sulphur  dioxide  is  passed 
into  the  diazo  solution  until  it  is  almost  saturated,  the  temperature 
being  kept  below  0° ;  without  stopping  the  stream  of  the  gas  copper 
powder  is  added  slowly  until  nitrogen  ceases  to  be  evolved.  The  whole 
is  filtered  and  the  copper  washed  well  with  cold  dilute  ammonia. 
The  united  filtrates,  which  must  still  contain  an  excess  of  free  sulphuric 
acid,  are  treated  with  a  cone,  solution  of  ferric  chloride  until  precipitation 
is  complete.  Ferric  benzene  sulphinate  separates  and  is  converted 
into  the  free  acid  by  shaking  with  a  slight  excess  of  dilute  aqueous 
ammonia.  The  free  acid  separates  out  on  adding  cold  cone,  hydrochloric 
acid  to  the  filtrate. 

\NH2  ->    (~   _S>N2HS04   >    C  ^S02H. 


Strong  acid  ;  soluble  in  hot  water  and  in  alcohol ;  prisms  ;  M.P.  83c 
84°  ;  decomposes  above  100°.    (J.  C.  S.,  95,  342  ;  B.,  24,  716.) 
Preparation  302. — Naphthalene  1-4-Sulpho-Sulphinic  Acid. 

SOaH 

C10H8O5S2.  272. 


50  gms.  sodium  naphthionate  (see  p.  312)  are  diazotised  in  the  usual 
way  (see  p.  365).  The  diazonium  compound  separates  out.  Sulphur 
dioxide  is  then  passed  in  until  the  solution  is  saturated,  the  temperature 
being  kept  below  0°.  Copper  powder  (see  p.  504)  is  then  added  very 
gradually  until  the  evolution  of  nitrogen  ceases,  a  slow  stream  of  S02 
being  passed  through  during  the  addition.  The  whole  is  then  filtered, 
and  common  salt  is  added  to  saturate  the  filtrate,  when  the  sodium  salt 
of  14-sulpho-sulphinic  acid  separates,  and  after  filtration  is  recrystallised 


320 


SYSTEMATIC  OKGANIC  CHEMISTRY 


from  water.  The  free  acid  may  be  isolated  by  passing  hydrochloric  acid 
gas  into  the  solution  in  water  of  the  sodium  salt. 

NH2  N  =  NCI  S02H. 


S03H  S03H  SO3H 

Yield.— Almost  theoretical  (62  gms.).    (J.  C.  S.,  95,  342.) 
Reaction  CLV.   Action  of  Potassium  Xanthate  on  Diazonium  Compounds 
with  Subsequent  Hydrolysis  and  Oxidation.    (E.P.,  11865,  1892). 

/S  ■  /S 

C6H5N2C1  +  KSC  ->  C6H5SC 

\0C2H5  \0C2H5 
H20  0 

*    C6H5SH      ^*  CgH5S03II. 

Reaction  CLVI. — Action  of  Hydrogen  Sulphide  on  Diazonium  Com- 
pounds.   (B.,  29,  272.) 

In  neutral  solution  at  0°  diazo  sulphides  are  formed,  e.g., 

N02C6H4N2C1  ->  (N02C6H4N2)2S. 
p-nitro  -diazobenzene. 

In  hydrochloric  acid  solution  the  disulphide  is  ultimately  formed — 

(N02C6H4N2)2S2. 

On  heating  a  diazo  solution,  nitrogen  is  evolved,  and  a  mercaptan  is 
formed — 

K.N2C1  +  H2S  ->  E.SH. 

Preparation  303. — Thiosalicylic  Acid.  (l-Sulphydro-2-carboxyl 
benzene.) 

;h 

CvH602S.  154. 

COOH. 

10  gms.  anthranilic  acid  (see  p.  241)  are  dissolved  in  150  c.cs.  water 
and  5  gms.  hydrochloric  acid.    20  gms.  of  ice  are  added  and  the  whole 
diazotised  in  the  usual  way.    H2S  is  passed  through  the  diazo  solution 
until  the  yellow  precipitate  becomes  red. 
/N2SH 

C6H4  is  formed,  and  after  filtration  the  moist  precipitate  is 

\COOH 

dissolved  in  sodium  carbonate  solution,  and  heat  is  applied  until  a  test 
portion  gives  a  white  precipitate  with  hydrochloric  acid.  The  solution 
is  acidified  with  hydrochloric  acid  and  the  thiosalicylic  acid  filtered 
off  and  washed  with  cold  water. 

Insoluble  in  water  ;  M.P.  163°— 164°  ;  salts  amorphous.  (D.K.P., 
69073  ;  B.,  22,  2206  ;  31,  1666.) 


THE  LINKING  OF  SULPHUR  TO  CARBON 


321 


Reaction  CLVII.  Action  of  Hydrosulphides  on  Alkyl  Halides  or  Sulphates, 
or  on  Certain  Aromatic  Halogen  Derivatives. 

K.C1  +  KSH  ->  K.SH  +  KCL 

K.HS04  +  KSH  ->  K.SH  +  KHS04. 

/CI  /SH 

R               +  KSH  ->  R 

\C00H  .  \C00H. 

The  mercaptans  are  colourless  liquids,  mostly  insoluble  in  water, 
possessing  a  characteristic  disagreeable  odour. 

Other  methods  by  which  mercaptans  can  be  formed  are  : — 

1.  Action  of  KCNS  on  diazo  salts  and  subsequent  hydrolysis  (B.,  23, 

738). 

R.N2C1         R.CNS  — >  R.SH. 

2.  Action  of  KSH  on  diazo  salts  (B.,  20,  349). 

R.N2C1  ->  R.SH. 

3.  See  Reaction  CLVI. 

Preparation  304. — Thiosalicylic  Acid.    (See  Preparation  303.) 

50  gms.  o-chlor-benzoic  acid  are  dissolved  in  38-5  gms.  caustic  soda  solu- 
tion containing  13-5  gms.  caustic  soda.  100  gms.  of  sodium  hydrosulphide 
and  0-5  gm.  copper  sulphate  are  then  added,  and  the  whole  heated  with 
stirring  to  about  200°.  The  mass  becomes  dark  red  and  melts,  when  the 
temperature  is  raised  to  250°.  It  then  gradually  solidifies.  The  melt 
is  dissolved  in  a  litre  of  water  and  boiled  up  with  animal  charcoal,  if 
necessary,  and  the  thiosalicylic  acid  precipitated  from  the  filtrate  by  adding 
hydrochloric  acid. 
'  Yield.— Almost  theoretical  (48  gms.).    (D.R.P.,  189200,  205450.) 

Preparation  305. — Ethyl  Mercaptan. 

C2H5SH.       C2H6S.  62. 

50  c.cs.  cone,  sulphuric  acid  and  50  c.cs.  20%  oleum'  are  added  to 
100  c.cs.  99%  alcohol,  the  temperature  being  kept  below  70°.  The 
mixture  is  allowed  to  stand  overnight  in  a  freezing  mixture,  and  then 
poured  on  to  a  mixture  of  ice  and  8%  sodium  carbonate  solution,  with 
stirring.  The  neutral  solution  is  concentrated  until  a  crust  of  salt 
forms  on  the  surface.  Sodium  sulphate  separates  out  on  cooling  and  is 
filtered  off.  A  40%  solution  of  caustic  potash  in  water  is  saturated  with 
H2S,  the  volume  of  the  solution  being  \\  times  the  volume  of  the  filtrate. 
This  solution  of  potassium  sulphide  is  then  added  to  the  filtrate  and  the 
whole  gently  distilled,  when  the  ethyl  mercaptan  passes  over.  It  is 
shaken  up  with  cone,  caustic  soda  solution  to  separate  ethyl  sulphide. 
The  ethyl  mercaptan,  after  removing  the  oil,  is  precipitated  by  adding 
acid  to  the  alkaline  solution. 

C2H5OH  ->  C2H5.HS04  ->  C2H5.SH. 

Colourless  liquid  ;  almost  insoluble  in  water  ;  offensive  odour  ;  B.P.  36°. 
(A.,  34,  25.X 

S.O.C.  ,  Y 


322 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Reaction  CLVIII.  Action  of  Phosphorus  Pentasulphide  on  Acids  or 
Alcohols. 

5C2H5OH  +  P2S5  ->  C2H5SH  +  P205. 
5CH3COOH  +  P2S5  ->  CH3COSH  +  P205. 

The  oxygen  is  replaced  by  sulphur  with  the  formation  of  mercaptans 
and  thio-acids. 
Prepaeation  306. — Thioacetic  Acid. 

CH3COSH.       C2H4OS.  76. 

150  gms.  of  phosphorus  pentasulphide  are  ground  up  and  mixed  with 
an  equal  weight  of  glacial  acetic  acid  and  50  gms.  of  glass  beads.  The 
whole  is  placed  in  a  distilling  flask  of  at  least  1  litre  capacity,  fitted  with 
a  condenser  and  thermometer,  and  continuously  warmed  with  a  naked 
flame.  Heating  is  stopped  as  soon  as  the  reaction  begins,  which  is  allowed 
to  proceed  spontaneously,  heat  being  applied  when  it  moderates.  Much 
frothing  may  take  place.  The  reaction  is  stopped  when  the  thermometer 
reaches  103°  C.  and  the  product  fractionated. 

Yield. — 25%  theoretical  (47-5  gms.).  Evil-smelling  liquid,  decomposed 
by  water  ;  B.P.  93°.    (B.,  28,  1205.) 

Reaction  CLIX.  Action  of  Sulphonyl  Chlorides  on  Hydrocarbons  in 
presence  of  Aluminium  Chloride.    (B.,  26,  2940.) 

AICI3 

R.S02C1  +  C6H6  >  E.S02.C6H5  +  HC1. 

The  compounds  formed  are  termed  sulphones ;  they  are  also  formed 
by  the  action  of  cone,  and  fuming  sulphuric  acid  on  hydrocarbons  (see 
p.  305),  and  by  heating  aromatic  sulphonic  acids  with  an  aromatic 
hydrocarbon  in  presence  of  a  dehydrating  agent,  such  as  P205. 

P205 

E.S02OH  +  C6H6   >  K.S02.C6H5. 

The  interaction  of  halogen  compounds  and  the  salts  of  sulphinic  acids 
yields  the  same  products. 

R.S02Na  +  BrC6H5  — >  R.S02C6H5  +  NaBr. 

The  sulphones  are  inert  compounds,  and  are  of  little  importance. 
Reaction  CLX.    Action  of  Phosphorus  Pentasulphide  on  Ethers. 

(B.,  27,  1239.) 
Thio-ethers  are  obtained  according  to  the  equation  : 

5(C2H5)20  +  P2S5  ->  5(C2H5)2S  +  P205. 

The  thio-ethers  are  neutral  volatile  compounds  of  little  importance. 
Reaction  CLXI.   Action  of  Sodium  or  Potassium  Sulphide  on  Alkyl 
Halides  or  Alkyl  Sulphates.    (B.  27,  1239.) 
Thio-ethers  are  obtained. 


2C2H5I  +  K2S       (C2H5)2S  +  2KI. 
2C2H5.S04K  +  K2S  ->  (C2H5)2S  +  2K2S04. 


CHAPTER  XXII 


THE  LINKING  OF  HALOGEN  TO  CARBON 

Reaction  CLXII.   Replacement  of  Oxygen  and  Hydroxyl  by  Halogens.— 

The  oxygen  of  ketone  and  aldehyde  groups  is  readily  replaced  by  halogen 
under  the  influence  of  phosphorus  trichloride  or  pentachloride  ;  the 
reaction  may  be  carried  out  with  or  without  a  solvent ;  solvents  commonly 
employed  are  chloroform,  benzene,  petroleum  ether,  acetyl  chloride  and 
phosphorus  oxy chloride. 

Alcoholic  hydroxyl  may  be  replaced  by  halogen  : — 

(a)  With  halogen  acids. 

The  action  is  slow  with  hydrochloric  acid,  heating  under  pressure  or 
the  use  of  a  dehydrating  agent  being  usually  necessary.  Hydrobromic 
acid  reacts  more  easily  and  hydriodic  still  more  easily.  Instead  of  the 
acids,  bromine  and  iodine  may  be  allowed  to  act  on  the  alcohols  in  presence 
of  phosphorus. 

(b)  With  phosphorus  oxychloride,  phosphorus  pentachloride,  phosphorus 
trichloride  or  tribromide,  or  sulphur  monochloride. 

The  pentachloride,  trichloride  and  tribromide  of  phosphorus  are  also 
used  for  replacing  hydroxyl  by  halogen  in  phenols,  carboxylic  acids  and 
sulphonic  acids.  The  use  of  phosphorus  trichloride  is  to  be  preferred  in 
the  preparation  of  many  acid  chlorides,  since  three  molecules  of  acid 
chloride  are  then  formed  per  molecule  of  phosphorus  halide,  as  against 
one  molecule  of  acid  chloride  when  the  pentachloride  is  used  : 

3R.COOH  +  PC13  ->  3R.CO.C1  +  H3P03. 
R.COOH  +  PC15  ->  R.CO.C1  +  POCI3  +  HC1. 

and  further,  no  volatile  compound  of  phosphorus  is  formed.  Phosphorus 
tribromide,  and  not  the  pentabromide,  is  generally  used  for  the  preparation 
of  acid  bromides.  Thionyl  chloride  does  not  react  with  aldehydic  and 
ketonic  groups,  but  reacts  readily  with  carboxyl  groups,  and  sometimes 
with  alcoholic  hydroxyl  groups. 

2R.COOH  +  SOClo  ->  2KCOC1  +  S02  +  H20. 

Excess  of  the  reagent  (SOCl2),  without  solvent,  is  generally  employed, 
and  the  excess  removed  by  distillation  or  by  treatment  with  formic  acid. 

Other  compounds  used  for  replacing  hydroxyl  by  halogen  are  carbonyl 
chloride,  benzenesulphonyl  chloride  and  sulphuryl  chloride. 

Preparation  307. — Benzophenone  Chloride  (Diphenyl-dichlor-methane). 

(C6H5)2CC12.       C13H10C12.  237. 

24  gms.  (1  mol.)  of  benzophenone  are  renuxed  with  40  gms.  (excess)  of 
phosphorus  pentachloride  on  an  oil  bath  at  220° — 240°  for  4  hours.  The 

323  y  2 


324 


SYSTEMATIC  ORGANIC  CHEMISTRY 


mixture  is  fractionally  distilled  under  reduced  pressure,  the  fraction 
boiling  at  193°  at  30  mms.  being  retained.  It  is  redistilled  under  reduced 
pressure. 

(C6H5)2CO  +  2PC15  =  (C6H5)2CC12  +  POCl3. 

Colourless  oil ;  B.P.3a  193°  ;  B.P.760  3  05°,  with  decomposition  ;  D.1845 
1-235.    (B.,  3,  752  ;  29,  2944.) 
Preparation  308. — Hippuryl  Chloride. 

C6H5.CONH.CH2.COCl.       C9H802NC1.  197-5. 

In  this  preparation  moisture  must  be  excluded  as  far  as  possible. 

5  gms.  (1  mol.)  of  hippuric  acid  are  finely  ground  and  passed  through  a 
fine  sieve.  The  powder  is  added  to  a  solution  of  6-5  gms.  (excess)  phos- 
phorus pentachloride  in  50  gms.  of  acetyl  chloride  contained  in  a  strong 
glass  bottle.  The  bottle  is  fitted  with  a  good  stopper  and  agitated  in  a 
shaking  machine  for  2  hours.  The  crystals  formed  are  filtered  off,  washed 
with  petroleum  ether,  and  dried  in  a  vacuum  desiccator  containing 
sulphuric  acid.  The  product  may  be  recrystallised  from  warm  acetyl 
chloride  (i.e.,  heated  on  a  water  bath)  ;  a  higher  temperature,  or  very 
prolonged  heating,  brings  about  some  decomposition. 

C6H5.CO.NH.CH2.COOH  +  PC15  ->  C6H5CO.NH.CH2.COCl  +  P0C13  +  HC1. 

Yield. — 80%  theoretical  (4-5  gms.).  Colourless  needles  ;  becomes 
yellow  at  125°,  then  dark  red,  and  melts  at  a  higher  temperature  ;  with 
alcohol  or  water  yields  hippuric  acid.    (B.,  38,  605.) 

Preparation  309. — Benzoyl  Chloride  (Acyl  chloride  of  benzoic  acid). 

C6H5C0C1.       C7H50C1.  140-5. 

50  gms.  (1  mol.)  of  phosphorus  pentachloride  are  weighed  by  difference 
in  a  fume  cupboard  into  a  250-c.c.  distilling  flask.  28  gms.  (1  mol.)  of 
benzoic  acid  are  added.  Dense  clouds  of  hydrogen  chloride  are  evolved 
during  the  reaction,  and  when  this  is  over,  the  contents  of  the  distilling 
flask  are  fractionally  distilled,  the  phosphorus  oxychloride  which  passes 
over  about  107°  being  rejected,  and  the  fraction  190° — 200°  collected 
separately. 

C6H5COOH  +  PC15  -  C6H5C0C1  +  POCl3  +  HC1. 

Yield. — 75%  theoretical  (25  gms.).    Colourless  liquid  ;  pungent  smell  ; 
fumes  in  moist  air  ;  B.P.  198-5°  ;  D.]|  1-214.    (A.,  3,  262  ;  60,  255.) 
Preparation  310. — Acetyl  Chloride  (Ethanoyl  Chloride). 

CH3COCI.       C2H30C1.  78-5. 

50  gms.  (excess)  of  glacial  acetic  acid  are  placed  in  a  250-c.c.  distilling 
flask  connected  by  a  water  condenser  with  another  distilling  flask  the 
side  of  which  is  fitted  with  a  calcium  chloride  tube.    40  gms.  of  phosphorus 


THE  LINKING  OF  HALOGEN  TO  CARBON  325 


trichloride  (2  mols.)  are  slowly  added  through  a  dropping-funnel,  the 
distilling  flask  being  cooled  in  a  cold  water  bath.  The  latter  is  then  heated 
at  45°  (caution  !)  until  the  evolution  of  hydrogen  chloride  diminishes 
when  the  water  bath  is  heated  to  boiling  till  nothing  further  distils.  The 
acetyl  chloride  contains  some  phosphorus  trichloride,  so  it  is  redistilled 
from  the  collecting  flask  over  fused  sodium  acetate,  the  fraction  53° — 56° 
being  separately  collected  in  the  same  way  as  before. 

3CH3COOH  +  PC13  =  3CH8C0C1  +  H3PO3. 

Yield. — 55%  theoretical  calculated  on  acetic  acid  taken  (45  gms.). 
Colourless,  pungent  smelling  liquid  ;  fumes  in  moist  air  ;  B.P.  55°  ; 
D.2;»  1-105.    (A.  Ch.,  [3],  37,  285  ;  C.  r.,  40,  944  ;  42,  224.) 

The  presence  of  phosphorus  trichloride  in  the  first  distillate  may  be 
proved  by  adding  a  few  drops  of  water  to  a  drop  of  the  distillate  (caution  !), 
oxidising  the  phosphorous  acid  formed  to  phosphoric  acid  by  boiling  with 
nitric  acid,  and  the  testing  with  ammonium  molybdate.  The  acetyl- 
phosphorous  acid  remaining  in  the  residue  from  the  second  distillation 
can  be  proved  to  be  present  by  evaporating  with  water  on  a  water  bath 
till  the  smell  of  acetic  acid  disappears,  and  then  testing  for  phosphoric 
acid  after  treatment  with  nitric  acid. 

Preparation  311. — o-Nitrobenzyl  Chloride  (l-Chlorometliyl-2-nitrc- 
benzene). 

C6H4(CH2C1)N02[1.2].       C7H602NC1.  171-5. 

10  gms.  of  o-nitrobenzyl  alcohol  (2  mols.)  dissolved  in  100  gms.  dry 
chloroform  are  placed  in  a  flask  in  a  fume  cupboard.  The  flask  is  well 
cooled  and  6  gms.  (approx.  1  mol.)  of  powdered  phosphorus  pentachloride 
added.  When  the  reaction  is  over  cold  water  is  added,  and  the  mixture 
shaken.  The  chloroform  layer  is  then  separated,  the  chloroform  removed 
by  distillation  and  the  residue,  after  solidification,  crystallised  from 
chloroform. 

N02C6H4.CH2OH  +  PC15    ->    N02C6H4.CH2C1  +  HC1  +  POCl3. 

Pale  yellow  needles  ;  M.P.  49°.    (B.,  18,  2402.) 

Preparation  312. — 2.6-Dichloruric  Acid  (2.6-Dichlor-S-oxy-punne). 

N  =  C.C1 

I 

C1C  C-NH 

\3.OH.       C5H2ON4CL.  205. 
N  —  C  N 

20  gms.  (3  mols.)  of  dry  potassium  urate  and  24  gms.  (excess)  of  phos- 
phorus oxy chloride  are  heated  in  a  sealed  tube  for  6  hours  at  160° — 170°. 
When  cold,  the  tube  is  carefully  opened  and  the  product  poured  into  water. 
The  precipitate  formed  is  filtered  off,  dried  and  powdered.    It  is  then 


326 


SYSTEMATIC  ORGANIC  CHEMISTRY 


added  slowly  to  5  parts  of  cone,  nitric  acid  and  boiled  for  20  minutes. 
Only  a  small  portion  of  the  dichloruric  acid  goes  into  solution,  and  this  is 
reprecipitated  by  diluting  with  water.  The  crude  acid  is  collected,  well 
washed  with  water,  and  while  suspended  in  24  parts  of  boiling  alcohol, 
is  treated  with  ammonia  solution  until  all  save  a  slight  impurity  is  dis- 
solved. Animal  charcoal  is  added  and  the  whole  boiled  and  filtered. 
The  ammonium  salt  of  the  acid  separates  out  in  pale  yellow  leaflets  on 
cooling,  and  further  crops  may  be  obtained  by  concentrating  the  mother 
liquors.  The  salt  is  redissolved  in  water,  and  the  free  acid  obtained  by 
precipitation  with  mineral  acid. 

3C5H403N4  +  2P0C13  ->  3C5H20N4C12  +  2H3P04. 

Yield. — 35%   theoretical   (7   gms.).    Colourless   crystalline  powder 
which  does  not  melt.    (B.,  30,  2208.) 
Preparation  313— Diphenyl  Chlor acetic  Acid. 

(C6H5)2C(Cl).COOH.       C14Hn02Cl.  246-5. 

15  gms.  (1  mol.)  benzilic  acid  and  15  gms.  (excess)  phosphorus  oxy- 
chloride  are  gently  warmed  together  until  a  slight  red  colour  appears. 
The  melt  is  then  cooled  and  shaken  with  a  litre  of  cold  water  until  (1 — 2 
hours)  the  product  becomes  quite  solid.  It  is  then  filtered  off,  washed 
with  water  and  dried.  It  is  purified  by  recrystallisation  from  a  mixture 
of  benzene  and  petroleum  ether. 

3(C6H5)2C(OH).COOH  +  POCl3  ->  3(C6H5)2C(Cl)COOH  +  H3P04. 

Yield.— 65%  theoretical  (14  gms.).    Rhombic  plates;   M.P.  118°— 
119°,  with  decomposition.    (B.,  36,  145.) 
Preparation  314. — /?-Iodo  Propionic  Acid  (3-Iod-pentan  acid). 

CHJ.CH2.COOH.       C3H502I.  200. 

100  gms.  (a  little  more  than  1  mol.)  of  phosphorus  di-iodide  (see  p.  507) 
are  added  in  small  quantities  to  52  c.cs.  (2  mols.)  of  glyceric  acid  (D.  1-26) 
in  a  large  round  flask,  and  the  mixture  gently  heated  till  a  violent  reaction 
sets  in.  Should  it  become  too  violent  the  flask  is  cooled  in  water.  The 
product,  a  dark  brown  syrupy  liquid,  is  again  heated,  when  a  second 
less  violent  reaction  occurs,  and  a  light  yellow  liquid,  which,  on  cooling, 
solidifies  to  a  crystalline  mass,  is  formed.  From  this  iodo propionic  acid 
is  extracted  with  hot  carbon  bisulphide  (caution!)  or  petroleum  ether 
(caution!).  The  solvent  is  distilled  off  and  the  discoloured  residue 
recrystallised  from  carbon  bisulphide  or  petroleum  ether. 

CH2(OH).CH(OH.).COOH  +  3HI  -  CH2I.CH2.COOH  +  2H20  +  I2. 

Colourless  pearly  laminae  ;  slightlv  soluble  in  cold,  readily  in  hot  water 
and  in  alcohol ;  M.P.  83-5°.    (A.,  131,  323  ;  166,  1  ;  B.,  9,  1902.) 


THE  LINKING  OF  HALOGEN  TO  CARBON 


327 


Preparation  315.— Menthyl  Chloride  (l-Methyl-4-(l-methyl-ethyl)-3- 
chlor-R-hexen). 

CH(CH3)2 


C10H19C1.  174-5. 


CH 

CHCl^CH, 

^H2X^^CH2 
CH 

CH3 

50  gms.  (1  mol.)  phosphorus  pentachloride  are  covered  with  dry 
petroleum  ether  in  a  flask  and  the  whole  w^ell  cooled  in  ice.  50  gms.  (excess) 
of  menthol  are  added  in  small  portions  to  the  cooled  mixture,  no  fresh 
menthol  being  added  until  the  evolution  of  hydrochloric  acid  has  ceased. 
The  petroleum  ether  is  then  distilled  off,  and  the  residue  distilled  with 
the  aid  of  a  fractionating  column  ;  crude  menthyl  chloride  passes  over  at 
205° — 215°,  and  it  may  be  purified  by  redistilling  several  times.  In  the 
crude  state  it  may  be  used  for  Preparation  443. 

C10H19OH  +  PC15  ->  C10H19C1  +  POCl3  +  HC1. 

Yield. — 55%  theoretical  (30  gms.).  B.P.  209-5°— 210-5°.  (B.,  29, 
317  ;  25,  686  ;  J.  C.  S.,  41,  54.) 

Preparation  316.  —  a-a-Propenyl-dichlorhydrin  (1.3-Dichlor-2-pro- 
panol). 

CH2C1.CH(0H).CH2C1.       C3H60C12.  129. 

Method  I. — 100  gms.  (1  mol.)  of  glycerol  are  dehydrated  by  gradually 
warming  on  a  sand  bath  to  175°.  When  cold  it  is  mixed  with  80  c.cs. 
of  glacial  acetic  acid,  and  a  stream  of  dry  hydrochloric  acid  is  conducted 
through  the  cold  liquid  for  about  2  hours  until  no  more  is  absorbed. 
The  mixture  is  heated  on  a  water  bath,  and  after  standing  at  room 
temperature  for  24  hours,  the  stream  of  hydrochloric  acid  is  again 
passed  through  for  6  hours.  The  product  is  then  distilled  ;  hydrogen 
chloride  and  dilute  acetic  acid  pass  over  first,  and  as  the  temperature 
rises  propenyl  dichlorhydrin  and  aceto-dichlorhydrin  distil.  The  fraction 
160° — 220°  is  redistilled  with  the  aid  of  a  column  until  a  fraction  of  boiling 
point  175°— 177°  is  obtained. 

CH2(OH).CH(OH).CH2(OH)  +  2HC1  ->  CH2C1.CH(0H).CH2C1  -f  2H20. 

Yield.— 70%  theoretical  (100  gms.). 

Method  II. — 125  gms.  (less  than  2  mols.)  of  sulphur  monochloride  (p.  507) 
are  slowly  added  in  small  quantities  at  a  time  from  a  tap  funnel  to  50  gms. 
of  anhydrous  glycerol  (dehydrated,  as  in  Method  I.)  contained  in  a  retort 
fitted  with  a  reflux  condenser.  The  experiment  should  be  conducted  in 
a  fume  chamber.  The  retort  is  occasionally  shaken,  and  the  reaction 
is  completed  by  heating  in  a  boiling  brine  bath  until  the  evolution  of 
hydrogen  chloride  from  the  condenser  has  almost  ceased.  The  condenser 
is  then  removed  and  the  mass  again  heated  until  all  sulphur  dioxide  and 


328 


SYSTEMATIC  ORGANIC  CHEMISTRY 


hydrogen  chloride  are  expelled.  When  cold,  the  semi-solid  mass  is  twice 
extracted  with  twice  its  volume  of  ether.  The  ethereal  extract  is 
filtered  free  from  sulphur,  and  the  ether  removed  by  distillation  on  a 
water  bath.  The  residue  is  repeatedly  fractionated  until  a  fraction  of 
boiling  point  175°— 178°  is  obtained. 

CH2(OH)CH(OH)CH2(OH)  +  2S2C12  -> 
CH2C1.CH(0H)CH2C1  +  2HC1  +  SOa  +  3S. 

Colourless  ethereal  liquid  ;  easily  soluble  in  ether  ;  B.P.  176°  ;  D.  J  1-383. 
(J.,  13,  456  ;  A.  Spl.,  1,  221  ;  A.,*122,  73  ;  168,  42.) 
Preparation  317. — Isopropyl  Iodide  (2-Iod-propan). 

CH3.CHI.CH3.       C3H7I.  170. 

5-5  gms.  (1  atom)  of  yellow  phosphorus  are  added  in  small  pieces  to 
20  gms.  (excess)  of  glycerol,  20  c.cs.  of  water,  and  30  gms.  (excess)  of  iodine, 
in  a  retort  attached  to  a  condenser.  At  the  beginning  a  flash  of  light 
attends  the  introduction  of  each  piece  of  phosphorus.  The  retort  is 
shaken  vigorously  till  when  about  one-third  of  the  phosphorus  has  been 
added  the  iodine  has  all  dissolved.  The  remainder  of  the  phosphorus 
is  then  added  more  quickly.  The  contents  of  the  retort  are  distilled  till 
no  more  oily  drops  collect,  and  the  distillate  replaced  in  the  retort  and 
redistilled.  The  second  distillate  is  washed  with  water,  dilute  sodium 
hydroxide  solution,  and  again  with  water.  After  drying  over  calcium 
chloride  it  is  redistilled. 

CH2OH  CH2I  CH3 

3HI  !  2HI 

CHOH           >  CHI  — >  CHI 

1              ,  1  I 

CH,OH  CH2I  CH3 

Yield. — 70%  theoretical  (15  gms.).    Colourless  liquid  ;   insoluble  in 
water;  B.P.  89-5°  ;  D.  J  1-744.    (A.,  138,  364.) 
Preparation  318. — Ethyl  Bromide  (Monobrom-ethan). 

CH3.CH2.Br.        C2H5Br.  109. 

Method  I. — A  General  Method  for  the  Preparation  of  Alkyl  Bromides. — - 
The  details  of  this  preparation  are  very  similar  to  those  given  in  the  general 
method  for  the  preparation  of  alkyl  iodides  (see  p.  330).  10  gms. 
(excess)  of  red  phosphorus  and  50  gms.  (excess)  of  ethyl  alcohol  are  placed 
in  a  distilling  flask,  attached  to  a  condenser  and  receiver.  The  receiver 
consists  of  a  Buchner  flask,  attached  by  means  of  a  cork  to  the  end  of  the 
condenser,  its  side  tube  being  connected  with  a  soda-lime  tower  to  trap 
any  fumes  of  hydrobromic  acid.  A  tap-funnel  containing  65  gms.  (5  mols.) 
of  bromine  is  fixed  through  a  cork  in  the  neck  of  the  distilling  flask.  The 
flask  is  cooled  in  water,  the  bromine  slowly  added,  the  whole  left  for 
several  hours,  and  the  contents  of  the  flask  then  distilled  from  the  water 


THE  LINKING  OF  HALOGEN  TO  CARBON 


329 


bath  at  50°,  the  receiver  being  cooled  in  ice.  The  distillate  is  purified 
as  in  the  preparation  of  ethyl  iodide,  given  on  p.  331. 

5ROH  +  P  +  5Br  =  5R.Br  +  H3P04  +  H20. 

Yield. — Almost  theoretical  (80  gms.).  Colourless,  highly-refractive 
liquid  ;  characteristic  odour  ;  soluble  in  all  the  usual  organic  solvents  ; 
insoluble  in  water  ;  B.P. 7;"  38-8°  ;  D.  »£  147  ;  D.  °  1485.    (J.,  1857,  441.) 

Note. — The  other  alkyl  bromides  may  be  prepared  in  a  similar  manner, 
with  the  aid  of  the  table  of  boiling  points  given  below.  For  those  bromides 
which  boil  over  100°,  the  same  precautions  must  be  taken  as  detailed  in 
the  General  Method  for  the  Preparation  of  Iodides  (p.  330). 


Substance.  Boiling  Point. 


^-Propyl  bromide  .  .  71° 

w-Butyl  bromide    .  .  '  100° 

iso-Butyl  bromide    .  .  92° 

is-o-Amyl  bromide    .  .  120° 


(B.,  14,  608  ;  A.,  158,  161  ;  93,  114  ;  159,  73.) 

Method  II. — 100  gms.  (excess)  of  cone,  sulphuric  acid  and  60  gms. 
(excess)  of  absolute  alcohol  are  mixed  in  a  litre  distilling  flask,  cooled 
under  the  tap,  and  100  gms.  (1  mol.)  of  coarsely  powdered  potassium 
bromide  added.  The  flask  is  closed  by  a  cork,  and  attached  to  a  condenser 
leading,  by  means  of  an  adapter,  into  a  250-c.c.  conical  flask,  which  serves 
as  a  receiver.  Enough  water  is  poured  into  the  latter  to  close  the  end  of 
the  adapter.  The  distilling  flask  is  then  heated  on  a  sand  bath  until  no 
more  oil  distils,  the  receiver  being  meanwhile  cooled  in  ice.  Should  the 
reaction  mixture  threaten  to  froth  over  the  flask  must  be  raised  from  the 
sand  bath  for  a  moment.  The  ethyl  bromide  is  separated  in  a  funnel, 
washed  with  an  equal  bulk  of  dilute  sodium  carbonate  solution,  and  with 
water,  dehydrated  over  calcium  chloride,  and  distilled  on  a  water  bath, 
the  fraction  35° — 43°  being  retained.  Ethyl  bromide  prepared  by  this 
method  usually  contains  traces  of  ether.  A  new  and  better  method, 
which  gives  the  pure  substance,  is  given  below. 

C2H5OH  +  H2S04  =  C2H5.H.S04  +  H20. 
C2H5.H.S04  +  KBr  =  C2H5Br  +  KHS04. 

Yield.— 83%  theoretical  (75  gms.). 

Method  III. — A  mixture  of  20  gms.  (1  mol.)  of  ethyl  alcohol  and  300  gms. 
(4  mols.)  of  hydrobromic  acid  of  constant  boiling  point,  126°,  and  D.  149 
(for  preparation  see  p.  502)  are  gradually  heated  in  a  distillation  flask  or 
retort  connected  with  a  condenser.  The  heating  is  continued  until  no 
more  oily  drops  pass  over.  The  distillate  is  then  washed,  dried,  and  dis- 
tilled, as  above.  Only  a  small  portion  of  the  acid  distils  over,  and 
if  the  residue  left  in  the  flask  is  slowly  distilled  the  excess  of  hydrobromic 


330 


SYSTEMATIC  ORGANIC  CHEMISTRY 


acid  can  be  obtained  in  the  form  of  the  solution  of  constant  boiling 
point,  and  again  used. 

C2H5OH  +  HBr  =  C2H5Br  +  H20. 

Yield— 86%  theoretical  (41  gms.).  (Am.  Soc,  38,  640;  Bl.  [iv.j, 
9,  134.) 

Preparation  319. — Ethyl  Chloride  (Mono-chlor-ethan). 

CH3.CH2C1.       C2H5C1.  64-5. 

Dry  hydrogen  chloride  is  passed  through  a  trap  into  200  gms.  of  absolute 
alcohol  containing  100  gms.  of  fused  coarsely  powdered  zinc  chloride,  in 
a  500-c.c.  round-bottomed  flask  heated  on  a  water  bath  and  fitted  with 
an  upright  condenser,  from  the  top  of  which  the  vapour  is  led  into  a  conical 
flask  containing  water.  The  inlet  tube  is  cut  off  just  above  the  surface  of 
the  water.  Thence  the  vapour  passes  through  a  tower  filled  with  soda- 
lime,  and  finally  into  a  U  -tube  surrounded  by  ice,  and  fitted  with  an  open 
tube  at  its  lowest  point.  The  condensed  ethyl  chloride  drops  from  the 
bottom  of  the  U-tube,  and  is  collected  in  a  small  conical  flask  standing  in 
ice.  The  upright  condenser  returns  all  alcohol  to  the  flask.  The  excess 
of  hydrogen  chloride  which  passes  on  is  absorbed  by  the  water  in  the  conical 
flask,  and  what  remains  is  removed  in  the  soda-lime  tower.  A  fairly 
rapid  stream  of  gas  must  be  maintained  on  starting  or  the  alcohol  will  be 
sucked  back  into  the  trap.  The  passage  of  the  gas  is  continued  until  a 
sufficient  quantity  of  ethyl  chloride  has  been  obtained.  It  must  be 
stored  in  a  well-stoppered  bottle,  wrapped  in  a  cloth,  and  placed  in  an 
ice  chest,  but  owing  to  the  risk  of  its  breaking  the  bottle  a  quantity  should 
only  be  kept  when  there  is  necessity  for  so  doing. 

C2H5OH  +  HC1  =  C2H5C1  +  H20. 

Yield. — Almost  theoretical  (280  gms.).  Colourless  liquid  ;  charac- 
teristic odour  ;  soluble  in  all  the  usual  organic  solvents  ;  insoluble  in 
water  ;  B.P.  12-5°  ;  D.  J  0-9214.  (A.,  150,  216  ;  174,  372  ;  Z.  Ch.,  1871, 
147.) 

Preparation  320.   Methyl  Iodide  and  Ethyl  Iodide. 

Methyl  iodide      CH3I.  142. 

Ethyl-iodide.       CH3.CH2I.       C2H5I.  156. 

A  General  Method  for  the  Preparation  of Alkyl  Iodides. — 36  gms.  (excess) 
of  methyl  alcohol  (52  gms.  of  ethyl  alcohol)  are  placed  in  a  500-c.c.  flask 
with  an  upright  condenser,  along  with  10  gms.  (excess)  of  red  phosphorus. 
100  gms.  (5  mols.)  of  powdered  iodine  are  slowly  added  during  1  hour  with 
frequent  shaking,  the  condenser  being  detached  from  the  flask  momen- 
tarily during  the  addition.  The  latter  is  cooled  in  cold  water  if  necessary. 
The  whole  is  then  allowed  to  stand  overnight,  or  should  that  time  be  not 
available,  it  is  left  for  3  hours  with  occasional  shaking,  and  then  gently 
boiled  on  a  water  bath  under  a  reflux  condenser  for  1  hour.  The  former 
method,  however,  gives  the  better  yield.  The  contents  of  the  flask  are 
then  distilled  oft  on  a  water  bath  into  a  receiver  containing  water  and 


THE  LINKING  OF  HALOGEN  TO  CARBON 


331 


cooled  in  ice ;  the  method  and  apparatus  described  in  Preparation  319 
may  be  used  . 

The  distillation  is  continued  till  the  greater  part  of  the  liquid  has 
distilled  over,  and  no  oily  drops  are  to  be  seen  in  the  condenser.  The 
residue  consisting  of  a  concentrated  solution  of  phosphorous  and  phosphoric 
acids  in  addition  to  excess  of  red  phosphorus  is  discarded.  The  distillate 
is  shaken  up  with  water  to  remove  alcohol,  and  then  with  dilute  caustic 
soda  to  remove  free  iodine.  Enough  alkali  must  be  used  to  render  the 
lower  layer  of  alkyl  halide  colourless.*  The  latter  is  then  separated  off, 
dried  over  granular  calcium  chloride  (6  gins.)  and  distilled.  The  prepara- 
tion should  be  kept  in  the  dark  in  a  well-stoppered  bottle.  If  exposed  to 
light,  iodine  slowly  separates,  but  may  be  prevented  from  so  doing  by 
adding  a  small  quantity  of  colloidal  silver  to  the  liquid. 

5ROH  +  P  +  51  =  5RI  +  H3P04  +  H20. 

Yield.— Almost  theoretical  (methyl  iodide,  90  gms.  ;  ethyl  iodide, 
100  gms.).  Colourless,  highly  refractive  liquids  ;  characteristic  odour  ; 
B.P.760  methyl  iodide,  42-8°  ;  B.P.760  ethyl  iodide,  72-2°;  D.J  methyl 
iodide  2-27  ;  D.'j  ethyl  iodide  1-975.  (A.  Ch.,  [1]  91,  89  ;  [2]  25,  323  ; 
42,  119  ;  A.,  126,  250  ;  J.  C.  S.,  117,  1592.) 

Note, — The  following  table  of  boiling  points  will  enable  the  iodides  in 
it  to  be  prepared  from  the  corresponding  alcohols.  In  distilling  off  the 
iodide  from  the  reaction  mixture  an  oil  bath  is  used  if  the  iodide  boils 
at  over  100°. 

Care  should  be  taken  not  to  raise  the  temperature  too  high,  as  there 
is  a  danger  that  the  red  phosphorus  may  take  fire  if  air  leaks  in.  To  avoid 
this  the  distillation,  if  not  done  on  a  water  bath,  is  best  carried  out  in  a 
current  of  carbon  dioxide. 


Compound. 

Boiling  Point. 

^-Propyl  iodide 
n-Butyl  iodide 
iso-Butyl  iodide 
150- Amy  1  iodide 

102° 
130° 
120° 
148° 

Reaction  CLXIII.  Addition  of  Halogen  or  Halogen  Hydride  to  Unsatu- 
rated Compounds. — Unsaturated  compounds  readily  combine  with  chlorine, 
bromine,  hydriodic  or  hydrobromic  acid.  The  addition  of  iodine  or  of 
hydrochloric  acid  is  generally  a  matter  of  difficulty.  The  unsaturated 
terpenes,  however,  unite  readily  with  hydrochloric  acid.  In  the  addition 
of  halogen  hydrides  to  unsaturated  hydrocarbons,  the  halogen  attaches 
itself  to  the  carbon  atom  having  the  lesser  amount  of  hydrogen  ;  with 

*  Should  difficulty  be  experienced  in  freeing  the  liquid  of  iodine,  addition 
of  a  little  sodium  thiosulphate  solution  is  extremely  effective. 


332 


SYSTEMATIC  ORGANIC  CHEMISTRY 


hydrocarbons,  containing  the  group  —  C  ==  C  — ,  two  atoms  of  halogen 
are  fixed  to  the  carbon  atom  having  the  lesser  amount  of  hydrogen. 
In  the  addition  of  halogen  hydrides  to  unsaturated  acids  and  aldehydes, 
the  halogen  generally  enters  the  ^-position. 

CH2  :  CH.COOH  +  HC1  ~>  CH2Cl.CH2.COOH. 

In  many  of  these  reactions  a  solvent  is  employed,  either  for  the  purpose 
of  dissolving  a  substance  or  for  moderating  the  action  of  the  reagent. 
Where  the  reagent  is  used  in  the  gaseous  form  its  action  may  be  moderated 
by  previous  admixture  with  an  inert  gas,  e.g.,  carbon  dioxide  or  air. 

Preparation  321. — Ethylene  Dibromide  (1.2-Dibrom-ethan). 

CH2Br.CH2Br.       C2H4Br2.  188. 

Ethylene  is  prepared  by  gently  heating  a  mixture  of  25  gms.  ethyl 
alcohol,  150  gms.  cone,  sulphuric  acid,  and  a  little  sand,  in  a  2-litre  round 
flask  on  a  sand  bath  till  a  steady  stream  of  gas  is  evolved.  A  mixture 
of  1  part  of  alcohol  and  2  parts  by  weight  of  cone,  sulphuric  acid  is  then 
slowly  added  through  a  tap-funnel,  the  lower  opening  of  which  has  been 
drawn  out  somewhat,  at  such  a  rate  that  the  gas  is  constantly  evolved 
without  frothing.  The  gas  is  purified  by  passing  it  through  two  wash- 
bottles  in  series  containing  dilute  caustic  soda  solution,  to  which  a  little 
phenolphthalein  has  been  added.  The  wash-bottles  are  fitted  with 
safety  tubes,  and  their  contents  must  be  renewed  occasionally,  the  phenol- 
phthalein serving  to  show  when  they  are  becoming  exhausted.  The  gas 
is  then  bubbled  slowly  through  two  wash-bottles  with  ground  glass 
stoppers,  each  containing  15  gms.  of  bromine  (1  mol.)  and  50  c.cs.  of  water, 
and  immersed  in  water,  the  temperature  of  which  is  kept  below  25°. 
Should  the  contents  of  the  ethylene  generating  flask  char  too  badly  (some 
charring  is  inevitable)  a  fresh  supply  of  gas  must  be  made.  When 
decolorisation  of  the  bromine  is  complete  (several  hours)  the  crude 
ethylene  bromide  is  washed  with  dilute  caustic  soda  solution  and  with 
water,  dried  over  calcium  chloride  and  distilled*,  •  the  fraction  130° — 132° 
being  collected  separately. 

CH3CH2OH  -  H20  =  CH2  :  CH2. 
CH2  :  CH2  +  Br2  =  CH2Br.CH,Br. 

Yield. — 85%  theoretical  (30  gms.).  Colourless  oil ;  insoluble  in  water  ; 
B.P.  760  131-5  ;  D.  ]!  2-19.    (A.,  168,  64.) 

Preparation  322. — Cinnamic  Acid  Dibromide  (3-Phenyl-2-3-dibrom- 
propan  acid). 

C6H5.CHBr.CHBr.COOH.       C9H802Br2.  308. 

Method  I. — 40  gms.  (1  mol.)  of  finely  divided  cinnamic  acid  are  spread 
out  on  a  large  clock-glass  and  placed  in  a  desiccator  over  concentrated 
sulphuric  acid.  A  dish  containing  45  gms.  (slightly  more  than  1  mol.)  of 
dry  bromine  is  supported  on  a  glass  tripod  above  the  cinnamic  acid,  the 
desiccator  is  closed,  and  allowed  to  stand  until  all  the  bromine  has  evapo- 
rated from  the  dish,  and  has  been  absorbed  from  the  acid  (about  3  days). 


THE  LINKING  OF  HALOGEN  TO  CARBON 


333 


The  clock-glass  is  removed,  the  product  exposed  to  the  air  for  several 
hours,  weighed  in  order  to  make  sure  that  the  theoretical  amount  of 
bromine  has  been  absorbed,  and  recrystallised  from  dilute  alcohol. 

C6H5.CH  :  CH.COOH  +  Br2  =  C6H5CHBr.CHBr.COOH. 

Yield.— Theoretical  (80  gms.).  Colourless  leaflets  ;  M.P.  195°  (decom- 
position)    (J.  C.  S.,  83,  669.) 

Method  II. — 12-5  gms.  (1  mol.)  of  cinnamic  acid  are  dissolved  in  65  c.cs. 
of  anhydrous  ether,  and  the  solution  cooled  to  0°  in  a  freezing  mixture. 
4-3  c.cs.  (1  mol.)  of  bromine  are  then  slowly  added  from  a  burette  while 
all  but  diffused  daylight  is  excluded,  as  the  reaction  is  very  violent  in 
direct  sunlight.  The  ether  is  removed  on  a  water  bath,  and  the  residue 
recrystallised  from  dilute  alcohol. 

Yield.— Theoretical  (25  gms.).    Colourless  leaflets.    (A.,  195,  140.) 

Preparation  323. — Dichlor-cinnamic  Acid  ( 4-Pheny  1-2.3 -dichlor- 
propan  acid). 

C6H5.CHC1.CHC1.C00H.       C9H802CL>,  219. 

Direct  sunlight  or  some  other  source  of  ultra-violet  rays  is  essential  for 
this  preparation. 

10  gms.  of  finely  ground  cinnamic  acid  are  suspended  in  80  gms.  of 
freshly  distilled  carbon  disulphide  in  a  quartz  flask.  A  stream  of  dry 
chlorine  gas  (p.  502)  is  passed  in  until  the  liquid  assumes  a  greenish-yellow 
colour.  The  mixture  is  alternately  shaken  until  this  colour  disappears, 
and  resaturated  with  chlorine  gas  until  an  increase  in  weight  of  5  gms. 
has  taken  place.  The  precipitate  is  filtered  off  and  recrystallised  from 
aqueous  alcohol. 

C6H5CH  :  CH.COOH  +  Cl2  ->  C6H5CHC1.CHC1.C00H. 

Yield.— 90%  theoretical  (14  gms.).  Colourless  leaflets  ;  M.P.  162°— 
164°  (slight  decomposition).    (B.,  14,  1867.) 

Preparation  324.— ft  -Phenyl-/?- Bromo  Propionic  Acid  (3-Phenyl-3- 
brom-propan  acid). 

C6H5CHBiCH2COOH.        C9H902Br.  229. 

10  gms.  (1  mol.)  of  finely  powdered  cinnamic  acid  are  heated  in  a  sealed 
tube  (see  p.  38)  for  2  hours  at  100°  with  10  gms.  of  glacial  acetic  acid 
which  has  been  saturated  with  hydrogen  bromide  at  ordinary  temperature. 
(1  gm.  of  glacial  acetic  acid  dissolves  about  0-6  gm.  of  hydrogen  bromide, 
so  there  is  an  excess  of  the  latter  present.)  The  precipitate  is  recrystallised 
from  dry  carbon  bisulphide  (the  acid  is  readily  decomposed  by  water) 
in  which  cinnamic  acid  is  readily  soluble,  even  in  the  cold. 

C6H5CH  :  CHCOOH  +  HBr  =  C6H5CHBr— CH2COOH. 

Colourless  crystals  ;  soluble  in  hot,  slightlv  soluble  in  cold  carbon 
bisulphide  ;  M.P.  137°.    (B.,  11,  1221.) 


334 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  325— Dipentene  Hydrochloride (l-[l-En-l-methyl-ethyl]. 
4-methyl-4-chlor-cyclo-hexan) . 

CH3 
CC1 

CH/^CH, 

CH2i    JcH2        ciohitC1.  172-5. 

CH 

i 

CH.,  :  C.CH,. 


This  reaction  must  be  carried  out  in  a  fume  cupboard. 
r  20  gms.(l  mol.)  of  dipentene, which  has  been  thoroughly  dried  over  metallic 
sodium,  are  dissolved  in  an  equal  volume  of  dry  carbon  disulphide,  the 
solution  placed  in  a  dry  distilling  flask — the  side  tube  of  which  is  con- 
nected with  a  calcium  chloride  tube — and  a  current  of  dry  hydrogen 
chloride  (see  p.  502)  led  into  the  solution  through  the  neck  of  the  flask, 
which  is  meanwhile  surrounded  with  ice.  After  8  hours  the  operation 
is  interrupted,  the  carbon  disulphide  removed  on  a  water  bath,  and  the 
residue  fractionated  under  reduced  pressure,  the  fraction  97° — 98°  at 
11 — 12  mms.  being  retained. 

CH3 

I  ,CH3 
C  I 
/\  C-€l 
CH,  CH  CH/NCH- 

I  +  HC1  = 

CH2CH2  CH|  JCH 


CH  |CH 


CH3   C  CH2 


Colourless  liquid  ;  B.P.11  97-98°. 

Note.— Every  trace  of  moisture  must  be  excluded  m  this  preparation 
(A.,  270,  188.) 

Preparation  326.— Ethylene  Bichloride  (1.2-Dichlor-ethan). 

CH2C1 

|  C2H4C1,.  99. 

CH2C1. 

Ethylene  is  prepared  by  dropping  ethyl  alcohol  slowly  into  phosphoric 
acid  heated  to  about  210°.  The  gas  is  passed  first  into  an  empty  wash- 
bottle  surrounded  by  a  freezing  mixture,  and  then  through  a  second 
containing  cone,  sulphuric  acid.  The  gas  is  next  passed  into  antimony 
trichloride  at  40°— 50°,  through  which  dry  chlorine  is  also  passed.  The 
ethylene  dichloride  formed  is  distilled  from  the  antimony  trichloride. 

Sweet  smelling  liquid  ;  B.P.  85°.    (P.  A.,  13,  297.) 


THE  LINKING  OF  HALOGEN  TO  CARBON 


335 


Reaction  CLXIV.— Replacement  of  Hydrogen  by  Nascent  Halogen.— 

When  nascent  bromine  is  required,  sodium  bromide  and  bromate  are 
added  to  the  substance,  and  the  amount  of  sulphuric  acid  required  by  the 
following  equation  is  added  : — 

5NaBr  +  NaBr03  +  6H2S04  ->  6NaHS04  +  3H20  +  6Br. 

An  excess  of  bromate  and  sulphuric  acid  are  often  employed  to  react 
with  the  hydrobromic  acid  formed  during  the  bromination  of  the  sub- 
stance. 

K.H  +  2Br  — >  R.Br  +  HBr. 
HB1O3  +  5HBr  — >  6Br  +  3H20. 

Nascent  chlorine  or  iodine  can  be  generated  from  their  corresponding 
salts  in  a  similar  manner. 
Preparation  327.— Acet-p-Chlorauilide  (l-Chlor-4-acetamino-benzene). 

Cl<^       ^>NH.COCH3.       C8H80NC1.  169-5. 

20  gms.  of  alcohol  and  20  gms.  glacial  acetic  acid  are  mixed,  and  to 
this  is  added  10  gms.  (1  mol.)  of  acetanilide,  which  is  dissolved  by  gentle 
heat.  After  20  c.cs.  of  water  have  been  added  the  solution  is  heated  to  50°, 
when  200  c.cs.  of  a  cold  10%  solution  (a  slight  excess)  of  bleaching  powder 
are  added  gradually  with  continuous  stirring.  A  white  precipitate  is 
formed  which  is  filtered  off,  washed  with  water,  and  then  recrystallised 
from  alcohol,  animal  charcoal  being  added,  if  necessary. 

Cl2 

C6H5NH.COCH3  ->  C6H5NCl.COCH3  ~>  C1C6H,NH.C0CH3. 

Colourless  needles  ;  M.P.  179° — 180°  ;  soluble  in  alcohol,  ether,  and 
carbon  disulphide.    (G.,  28,  II.,  313.) 

Preparation  328.— 2.6-Dichlor-4-Nitraniline. 

CI 

NH</      ^>N02.       C6H402N2C12.  207. 
Cl~ 

35  gms.  of  p-nitraniline  are  dissolved  in  312  c.cs.  cone,  hydrochloric 
acid  at  50°.  A  solution  of  20-5  gms.  of  potassium  chlorate  in  437  c.cs. 
of  water  at  about  25°  are  slowly  added.  When  all  the  chlorate  has  been 
added  the  solution  is  diluted  with  a  large  quantity  of  water  ;  the  precipitate 
formed  is  removed  by  filtration  and  well  washed.  It  can  be  further 
purified  by  crystallisation  from  glacial  acid  or  from  a  mixture  of  glacial 
acetic  acid  and  alcohol. 

CI 

NH,/      ^>N02  +  Cl2    ->    NH2/  \>N02. 

CI 

Yield. — 87%  theoretical  (42  gms.).  Lemon-yellow  needles ;  M.P. 
185°— 188°.    (B.,  36,  4391.) 


33G 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  329. — Chloranil  (Tetra-chloro-^-benzquinone). 

Cl_  CI 

0  =  /        y=0.        C602C14.  246. 
CT~C1 

30  gms.  of  2.6-diclilor-4-nitraniline  are  boiled  with  750  c.cs.  of  cone, 
hydrochloric  acid  and  33  gms.  of  tin,  and  thus  reduced  to  the  corresponding 
diamine.  25  gms.  of  crystallised  potassium  chlorate  are  added  slowly, 
without  cooling,  the  whole  being  kept  gently  boiling.  The  boiling  is 
carried  on  for  a  short  time  after  the  whole  of  the  chlorate  has  been  added  ; 
the  liquid  is  then  diluted  and  filtered.  The  precipitate  is  washed  well  with 
water,  dried,  and  purified  by  recrystallisation  from  toluene  or  by  sublima- 
tion. 

CI  CI  CI  CI 

NH2/      \N02   ->    NH2/      )NH2    ->    0=/      \  =  0. 

ci  cr  cr~ci 

Yield. — 90%  theoretical  (32  gms.).  Yellow  leaflets ;  sublimes  on 
heating.    (B.,  36,  4390.) 

Reaction  CLXV.  Replacement  of  Hydrogen  by  the  Use  of  Halogen  Com- 
pounds.— The  halogen  compounds  used  are  those  of  phosphorus,  sulphur, 
antimony  and  iodine,  and  also  sulphuryl  chloride  and  bleaching  powder. 
When  phosphorus  pentachloride  is  used  the  halogen  does  not  enter  the 
nucleus  until  the  hydrogen  of  the  side  chain  has  been  completely  replaced. 
A  mixture  of  red  phosphorus  and  bromine  is  used  in  place  of  phosphorus 
bromide  ;  with  yellow  phosphorus  the  reaction  is  much  too  vigorous. 
As  red  phosphorus  generally  contains  traces  of  free  phosphoric  acid  it 
should  be  previously  washed  with  water  until  acid  free,  and  dried  before 
using.  Sulphur  bromide  and  iodide  are  used  in  presence  of  nitric  acid  ; 
with  these  the  halogen  enters  the  nucleus,  and  only  mono-derivatives 
are  formed.  Antimony  pentachloride  yields  two  atoms  of  halogen  for 
chlorination.  Iodine  monochloride  in  glacial  acetic  acid  or  dilute  hydro- 
chloric acid  replaces  hydrogen  by  iodine.  Sulphuryl  chloride  chlorinates 
aromatic  compounds,  both  in  the  side  chain  and  in  the  nucleus  ;  when 
a  carbonyl  or  carboxyl  group  is  present  the  hydrogen  in  the  a-position 
to  this  group  is  substituted.  Bleaching  powder  is  used  as  a  chlorinating 
agent  owing  to  the  ease  with  which  it  gives  up  its  available  chlorine. 

Preparation  330. — a-Bromo-stearic  Acid  (2-Brom-octa-decan  acid). 

CH3(CH2)15CHBrCOOH.       ClsH3502Br.  363. 

30  gms.  (3  mols.)  of  stearic  acid  and  1-1  gms.  (1  atom)  of  red  phosphorus 
are  placed  in  a  flask  fitted  with  a  reflux  condenser  and  dropping-funnel. 
The  flask  is  immersed  in  a  water  bath  containing  water  at  60° — 70°,  so 
that  the  stearic  acid  melts,  and  22-5  gms.  (4  mols.)  of  dry  bromine  are  added 
gradually  from  the  dropping-funnel.  When  addition  is  complete  the 
mixture  is  heated  on  a  boiling  water  bath  for  about  3  hours.    The  product 


THE  LINKING  OF  HALOGEN  TO  CARBON 


337 


is  poured  into  water,  and  the  monobromo stearic  acid  filtered  of!  and  dried 
on  a  porous  plate.    It  is  recrystallised  from  carbon  disulphide. 

3CH3(CH2)16COOH  +  P  +  4Br2  =  3CH3(CH2)15CHBrCOBr  +  HP03  +  2HBr. 
CH3(CH2)15CHBrCOBr  +  H20  ->  CH3(CH2)15CHBrCOOH. 

Colourless  plates  ;  M.P.  61°  ;  the  materials  used  in  this  preparation 
must  be  pure  and  dry  (see  preparation  of  mono-bromacetic  acid).  (B.,  24, 
2903  ;  25,  482.) 

Preparation  331. — Mono-bromacetic  Acid  (Mono-brom-ethan  acid). 

CH2BrCOOH.       C2H302Br.  139. 

The  materials  for  this  preparation  must  be  pure  and  dry.  The  acetic 
acid  is  purified,  as  on  p.  234  ;  the  bromine  is  shaken  with  cone,  sulphuric 
acid,  and  the  phosphorus  warmed  with  dilute  ammonia,  washed  well  with 
water,  and  dried  in  a  steam  oven. 

20  gms.  (3  mols.)  of  pure  glacial  acetic  acid  and  3  gms.  (1  atom)  of  red 
phosphorus  are  placed  in  a  round-bottomed  flask  of  about  300  c.cs. 
capacity.    (N.B. — Rubber  stoppers  should  not  be  used.) 

71  gms.  (4  mols.)  of  bromine  are  added  from  a  dropping  funnel  very 
gradually  at  first,  the  flask  being  cooled  by  immersion  in  cold  water. 
The  reaction  proceeds  with  great  vigour,  but  moderates  after  about  half 
of  the  bromine  has  been  added,  when  the  remainder  may  be  run  in  more 
quickly.  The  flask  is  then  warmed  on  a  boiling  water  bath  until  the  colour 
of  bromine  vapour  in  the  interior  of  the  flask  disappears.  After  cooling, 
the  brom-acetyl  bromide  is  poured  into  a  distilling  flask  and  distilled 
under  diminished  pressure. 

The  product  is  weighed,  and  the  theoretical  amount  of  water  required 
to  convert  it  into  bromacetic  acid  added  gradually  (1-8  gms.  for  20  gms. 
of  the  acyl  bromide).  The  mixture  solidifies  to  a  white  crystalline  mass. 
This  is  purified  by  distilling  under  ordinary  pressure  from  a  small  distilling 
flask  provided  with  an  air  condenser,  the  portion  distilling  at  190° — 210° 
being  retained. 

3CH3COOH  +  P  +  8Br  =  3CH2BrCOBr  +  HP03  +  2HBr 
CH2BrCOBr  +  H20  ~>  CH2BrCOOH. 

Yield.— Variable.    Colourless  crystals;    M.P.  50°— 51°  ;    B.P.  208°. 
Note. — The  bromacetyl  bromide  and  bromacetic  acid  must  not  be 
allowed  to  touch  the  hands  as  they  cause  serious  wounds. 
(B.,  20,  2026  ;  A.,  242,  141.) 

Preparation  332. — Mono-bromsuccinic  Acid  (2-Brom-butan-diacid). 

COOH.CH2.CHBrCOOH.       C4H504Br.  197. 

A  tubulated  retort  is  sealed  to  a  Liebig's  condenser,  and  the  latter 
connected  to  an  apparatus  to  absorb  hydrobromic  acid.  18  gms.  (3  mols.) 
of  carefully  dried  succinic  acid  are  intimately  mixed  with  3-5  gms.  (excess) 
of  red  phosphorus.  This  is  placed  in  the  retort,  and  80  gms.  (excess)  of 
bromine  is  added  slowly  from  a  dropping-funnel  through  the  tubulus. 
rhe  bromine  must  be  very  carefully  added  at  the  beginning  as  the  reaction 


338 


SYSTEMATIC  ORGANIC  CHEMISTRY 


is  violent,  and  again  added  only  when  the  reaction  subsides.  When  all 
the  bromine  has  been  added,  the  whole  is  heated  on  a  water  bath  until 
the  bromine  disappears.  The  retort  now  contains  mono-bromsuccinyl 
bromide  ;  the  free  acid  is  obtained  by  pouring  slowly  the  contents  of  the 
retort  into  100  c.cs.  of  boiling  water,  the  flame  being  withdrawn.  It  is 
then  filtered,  and  repeatedly  extracted  with  ether,  the  latter  removed  on 
the  water  bath,  and  the  residue  recrystallised  from  water. 

CHo.COOH  CH.Br.COBr 
3  1  +  2P  +  8Br2  — >  3  I  +  2HP03  +  7HBr. 

CH2.COOH  CH2.COBr 
CHBr.COBr  CH.Br.COOH 
|  +  2H20  ->  | 

CH2COBr  CH2COOH. 

Yield,— 85%  theoretical  (25  gms.).  Colourless  crystals  ;  M.P.  160°  ; 
soluble  in  water.    (A.,  242,  145  ;  B.,  14,  892.) 

Preparation  333. — 2.4,1-Iod-nitraniline  (l-Amino-2-iod-4-nitroben- 
zene). 

C6H3(NH2)(N02)I.       C6H502N2.I.  264. 

15  gms.  (1  mol.)  of  finely  ground  ip-m tramline  are  agitated  with  cold 
glacial  acetic  acid  in  quantity  just  sufficient  to  bring  all  into  solution. 
A  solution  of  26-5  gms.  (1  mol.)  of  iodine  monochloride  in  glacial  acetic 
acid  is  then  slowly  added  to  the  well-stirred  solution,  which  after  the 
addition  is  allowed  to  stand  1  hour.  It  is  then  poured  into  1-5  litres  of 
boiling  water,  filtered  and  allowed  to  cool.  After  some  time  crystals  of 
iod-nitraniline  separate  which  are  filtered  off  and  dried. 

C6H4(NH2)(N02)  +  IC1  ->  C6H3(NH2)(N02)I  +  HC1. 

Long,  yellow  needles  ;  soluble  in  hot  water  ;  M.P.  105°.  (B.,  34,  3344.) 
Preparation  334. — Mono-chlor-malonic  Acid  (2-Chlor-propan-diacid). 

CH.Cl(COOH)2.       C3H304C1.  138-5. 

8  gms.  (1  mol.)  of  malonic  acid  from  a  sample  which  had  been  dried  in  a 
steam  oven  and  cooled  in  a  desiccator  are  dissolved  in  250  c.cs.  of  anhydrous 
ether.  The  solution  is  cooled  in  ice  water,  and  10  gms.  (1  mol.)  of  sulphuryl 
chloride  slowly  added.  The  ether  is  removed  on  a  water  bath,  and  the 
residue  left  in  a  vacuum  desiccator  containing  sulphuric  acid  until  crystal- 
lisation of  mono-chlor-malonic  acid  is  complete. 

CH2(COOH)2  +  S02C12  ->  CHCl(COOH)2  +  HC1  +  S02. 

Yield.— Theoretical  (10-5  gms.).  Colourless  crystals;  M.P.  133°. 
(B.,  35,  1814.) 

Reaction  CLXVI.   Replacement  of  the  Amino  Group  by  Halogen. — 

The  amino  group  can  easily  be  replaced  by  halogen : — 

(a)  By  means  of  the  Sandmeyer  reaction.    The  amine  is  diazotised 

and  the  resulting  diazonium  solution  added  to  a  warm  solution  of  cuprous 

halide. 

E.NH2  ->  R.N  :  NCI  ->  R.C1  +  N2. 


THE  LINKING  OF  HALOGEN  TO  CARBON  339 


(b)  By  Gattermann's  method,  in  which  copper  powder  is  added  to  an 
acid  solution  of  the  diazonium  salt. 

(c)  By  heating  a  solution  of  the  diazonium  compound  with  hydriodic 
acid  or  potassium  iodide. 

Preparation  335. — o-Brom-toluene. 

C6H4(CH3).Br.       C7H7Br.  171. 

6  gms.  or^o-toluidine  are  dissolved  in  a  mixture  of  35  c.cs.  hydro  - 
bromic  acid  of  constant  boiling  point,  and  40  c.cs.  of  water.  The  solution 
is  cooled  to  0°,  and  diazotised  by  the  addition  of  5  gms.  sodium  nitrite 
dissolved  in  12  c.cs.  of  water  ;  during  this  addition  a  drop  is  frequently 
removed,  diluted  with  water  on  a  watch-glass,  and  tested  with  starch 
iodide  paper  for  free  nitrous  acid  (see  p.  365).  Copper  powder  (prepared 
from  40  gms.  copper  sulphate,  see  p.  504)  is  then  added  in  small  quantities 
at  a  time  to  the  diazonium  solution,  which  should  be  continuously  stirred  ; 
an  effervescence — due  to  the  escape  of  nitrogen — takes  place.  When 
addition  of  copper  produces  no  further  effervescence,  the  bromo-toluene 
forms  the  lower  layer.  This  layer  is  separated,  steam-distilled  and  the 
distillate  extracted  with  ether.  The  ethereal  solution  is  dried  over  solid 
calcium  chloride,  and  fractionated. 

CH8.C6H4.NH2  ->  CH3.C6H4N  :  N  ->  CH3.C6H4.Br. 

Br 

Yield.— 70%  theoretical  (6  gms.).    B.P.  181°.   (G.  (1890),  29,  631.) 
Preparation  336. — jo-Chlor-toluene  (l-methyl-4-chloro-benzene). 

CH3.C6H4.C1.       C7H7C1.  126-5. 

20  gms.  (1  mol.)  of  jo-toluidine  are  dissolved  in  100  c.cs.  of  a  mixture  of 
equal  volumes  of  water  and  cone,  hydrochloric  acid,  and  diazotised  in 
the  usual  way  (see  p.  365)  with  sodium  nitrite.  15  gms.  of  moist 
copper  powder  (see  p.  504)  are  then  added  in  small  portions  to  the  well- 
stirred  solution.  When  the  evolution  of  nitrogen  has  ceased,  the  product 
is  steam-distilled,  the  distillate  extracted  with  ether,  and  the  ethereal 
solution  dried  over  anhydrous  sodium  sulphate.  The  sodium  sulphate 
is  filtered  off  and  the  filtrate  distilled.  p-Chloi -toluene  passes  over  at  163°. 

CH3.C6H4.NH2  ->  CH3.C6H4N2C1  ->  CH3.C6H4C1  +  N2. 

Colourless  oily  liquid  ;  M.P.  7-4°  ;  B.P.  163°.    (B.,  23,  1218.) 
Preparation  337. — Chlorobenzene.  ' 

C6H5.C1.  112-5. 

20  gms.  aniline  are  dissolved  in  130  c.cs.  water  and  37  c.cs.  cone, 
hydrochloric  acid,  and  diazotised  (see  Preparation  378)  at  0° — 5°  by  the 
addition  of  15  gms.  sodium  nitrite  dissolved  in  40  c.cs.  water.  140  c.cs. 
of  a  10%  solution  of  cuprous  chloride  (p.  504)  are  heated  nearly  to 
boiling  in  a  flask  and  the  diazonium  solution  run  in  gradually,  the 
contents  of  the  flask  being  occasionally  shaken,  and  maintained  near 
boiling  during  the  addition. 

z  2 


340  SYSTEMATIC  ORGANIC  CHEMISTRY 


The  yellow  precipitate  which  appears  on  the  introduction  of  the 
diazonium  solution  decomposes  almost  immediately,  yielding  chloro- 
benzene  and  nitrogen.  The  contents  of  the  flask  are  submitted  to  steam 
distillation  until  no  more  oily  drops  of  chlorobenzene  pass  over.  The 
distillate  is  extracted  with  ether,  the  ethereal  solution  dried  oyer  calcium 
chloride  and  fractionated. 

G6H5N2C1^C6H5.C1  +  N, 

Yield.— 75%  theoretical  (18  gms.).    Colourless  liquid;    B.P.  132°. 
(B.,  23,  1880  ;  23,  1628  ;  A.,  272,  141.) 
Preparation  338 .— ^-Iodo-toluene. 

CH3.C6H4.1.       C7H7I.  171. 

20  gms.  of  ^-tohridine  are  boiled  with  hydrochloric  acid  to  dissolve  the 
base,  the  solution  being  distinctly  acid.  The  solution  is  diazotised  as 
usual,  and  when  diazotisation  is  complete  31  gms.  potassium  iodide 
dissolved  in  water  are  then  run  in  from  a  tap-funnel  with  continuous 
stirring.  The  mixture  is  allowed  to  stand  for  a  time  when  a  dark  brown 
mass  is  formed  which  is  filtered  off  and  recrystallised  from  alcohol. 

CH3C6H4NH2  ->  CH3C6H4N2C1  ->  CH3C6H4I. 

Yield.— 80%  theoretical  (25  gms.).  Yellow  plates ;  M.P.  35°  ; 
B.P.  211°. 

Reaction  CLXVII.  Replacement  of  Halogen  by  Halogen. — The  substi- 
tution of  bromine  by  chlorine  can  be  effected  through  the  use  of  the 
pentachlorides  of  antimony  or  phosphorus.  Iodine  is  still  more  readily 
replaced  by  chlorine,  not  only  by  direct  action  of  the  latter  but  also  by 
double  decomposition  with  certain  metallic  chlorides  (HgCl2,  SbCl5,  AgCl) 
or  iodine  trichloride. 

The  substitution  of  chlorine  by  the  direct  action  of  bromine  is  rarely 
effected.  Aluminium  bromide,  cupric  bromide  in  alcoholic  solution  or 
boron  tribromide  under  pressure,  convert  many  alkyl  chlorides  into  alky! 
bromides.  Mono-chloracetic  acid  heated  to  150°  in  a  sealed  tube  with 
hydrobromic  acid  or  potassium  bromide  yields  mono-bromacetic  acid. 

Iodine  may  be  replaced  by  bromine  by  direct  action  or  by  heating 
under  pressure  with  bromides  of  copper,  mercury,  silver  or  boron. 

Bromine  and  iodine  can  be  replaced  by  iodine  through  double  decom- 
position with  hydriodic  acid  or  iodides  of  potassium,  calcium  or  aluminium. 

Preparation  339. — Iod-acetic  Acid. 

CHJ.COOH.       C2H302r.  186. 

25  gms.  (1  mol.)  of  chloracetic  acid  dissolved  in  125  c.cs.  of  absolute 
alcohol  and  50  gms.  (excess)  of  finely-powdered  potassium  iodide  are 
refluxed  on  a  water  bath  for  1  hour.  The  product  is  well  cooled  in  ice 
water,  and  filtered  from  potassium  chloride  and  iodide.  The  filtrate  is 
decolorised  (if  necessary)  by  passing  in  a  stream  of  sulphur  dioxide,  and 
afterwards  evaporated  to  a  small  bulk  on  a  water  bath.    On  cooling,  a 


THE  LINKING  OF  HALOGEN  TO  CARBON 


341 


product  separates  which  is  collected,  dried  by  exposure  in  air,  and 
recrystallised  from  a  large  volume  of  petroleum  ether. 

CH2Cl.COOH  -f  KI  ->  CHJ.COOH  +  KC1. 

Colourless  leaflets  ;  M.P.  84°  ;  the  solid  Causes  painful  blisters  in  contact 
with  the  skin,  and  the  vapours  irritate  the  eyes.  (Z.  Ch.,  1868,  484  ; 
B.,  41,  2853.) 

Preparation  340. — Propenyl  Tribromide  (1.2.3-Tribrom-propan). 

CH2.Br.CHBr.CH2Br.       C3H5Br3.  281. 

75  gms.  (slight  excess)  of  bromine  are  slowly  added  to  50  gms.  (1  mol.) 
of  allyl  iodide  contained  in  a  flask,  fitted  with  an  air  condenser,  and  well 
cooled  in  a  freezing  mixture  ;  the  whole  apparatus  being  set  up  in  a  fume 
cupboard.  The  liquid  is  allowed  to  stand  24  hours,  and  filtered  from 
the  iodine  which  has  crystallised  out.  The  brown  filtrate  is  repeatedly 
washed  with  dilute  caustic  soda  solution,  and  finally  with  sodium  thio- 
sulphate,  and  then  with  water,  dried  over  fused  calcium  chloride  and 
distilled.  The  distillate  is  again  treated  with  sodium  thiosulphate 
solution  and  with  water,  dried  and  distilled.  The  fraction  200° — 220° 
is  allowed  to  stand  in  a  freezing  mixture,  and  the  mother  liquor  is  then 
poured  off  from  the  crystals  which  form.  The  product  is  purified  by 
repeated  distillations. 

CH2 :  CH.CH2I  +  3Br  =  CH2Br.CHBr.CH2Br  +  L 

Colourless  glistening  prisms  ;  insoluble  in  water  ;  M.P.  16°  ;  B.P.  219° — 
220°.    (A.  Ch.,  [3],  48,  304  ;  [3],  51,  91  ;  C.  r.,  70,  638  ;  A.,  156,  168.) 
Reaction  CLXVIII.   Replacement  of  Hydrogen  by  Molecular  Halogen. — 

Chloro-  and  bromo-derivatives  of  the  aliphatic  hydrocarbons  are  obtained 
by  the  action  of  chlorine  and  bromine  on  these  hydrocarbons  in  presence 
of  light,  the  reaction  being  more  energetic  in  sunlight  than  in  diffused 
light.  The  corresponding  iodo-derivatives  cannot  be  obtained  in  this 
way,  due,  it  is  supposed,  to  the  energetic  reducing  action  of  hydriodic 
acid,  which  converts  the  iodo-derivative  into  the  original  paraffin. 

CH4  +  I2  ->  CH3I  +  HI  ->  CH4  +  I2. 

In  the  case  of  aromatic  bodies  the  temperature  has  an  important 
influence  on  the  part  of  the  molecules  the  chlorine  or  bromine  will  attack  ; 
in  the  cold  in  the  presence  of  carriers,  the  halogen  enters  the  nucleus, 
while  at  the  boiling  point  the  side  chain  is  attacked.  The  carriers  most 
frequently  used  are  :  iron,  aluminium-mercury  couple,  iodine,  halides  of 
phosphorus  antimony,  iron  or  aluminium,  sulphur.  The  halogen  is  always 
more  active  in  sunlight,  or  in  ultra-violet  light. 

A  solvent  is  frequently  employed,  either  to  dissolve  the  compound  or 
to  moderate  the  action  of  the  halogen  ;  those  commonly  employed  are 
carbon  tetrachloride,  glacial  acetic  acid,  carbon  disulphide,  ethylene 
dichloride,  chloroform,  ether,  water,  hydrochloric  acid,  sulphuric  acid. 
It  is  not  always  a  matter  of  indifference  what  solvent  is  selected. 


342  SYSTEMATIC  ORGANIC  CHEMISTRY 


In  some  cases  the  operation  has  to  be  conducted  in  a  sealed  tube  under 
pressure,  and  if  a  solvent  is  also  employed  carbon  tetrachloride  is  generally 
the  most  suitable. 

Preparation  341. — Dibrom-sulphanilic  Acid  (2.6-Dibrom-l-amino-4- 
benzene  sulphonic  acid). 

C6H2Br2(NH2)(S03H).       C6H503NBr2S.  331. 

10  gms.  (1  mol.)  of  sulphanilic  acid  are  dissolved  in  about  1  litre  of 
warm  water.  The  solution,  when  cold,  is  placed  in  a  large  bottle  or  flask 
which  is  connected  to  a  suction  pump  on  one  side,  and  to  a  wash-bottle 
containing  18-5  gms.  (2  mols.)  bromine  on  the  other.  In  this  way  a 
stream  of  air  laden  with  bromine  vapour  is  drawn  through  the  solution. 
When  the  bromine  has  completely  disappeared,  the  liquid  is  filtered, 
and  concentrated  on  a  water  bath  until  a  sample  yields  a  large  crop  of 
crystals  on  cooling.  The  whole  is  allowed  to  cool,  the  crystals  separated 
and  dried.  The  mother  liquor  may  yield  a  second  crop  after  further 
concentration. 

C6H4(NH2)(S03H)  +  2Br2  ->  C6H2Br2(NH2)(S03H)  +  2HBr. 

Yield. — 90%  theoretical  (16  gms.).    Colourless  needles  ;    soluble  in 
hot  water  ;  decomposes  at  180°.    (A.,  120,  138.) 
Preparation  342.— Chlor-benzene  (Phenylchloride). 

C6H5C1.  112-5. 

100  gms.  of  pure,  dry  benzene  are  heated  to  boiling  with  1  gm.  wrought 
iron  powder  in  a  large  round-bottomed  flask  with  reflux  condenser 
attached.  A  stream  of  dry  chlorine  is  passed  through  at  a  temperature 
of  79°  with  vigorous  stirring.  It  is  essential  that  the  chlorine  should  be 
dried,  and  at  least  three  wash-bottles  of  cone,  sulphuric  acid  and  a  calcium 
chloride  tube  are  recommended.  The  hydrochloric  acid  evolved  during 
the  reaction  may  be  absorbed  in  a  flask  which  contains  a  layer  of  water. 
Chlorine  is  passed  in  until  about  90%  of  the  calculated  quantity  is  used 
up.  The  chlorination  lasts  about  5  hours,  and  the  weight  should  be 
increased  by  43  gms.  The  gas  should  be  well  regulated,  otherwise 
unchanged  benzene  will  be  carried  off.  If  the  chlorine  inlet  tube  becomes 
stopped  up  with  dichlor-benzene,  the  stream  of  gas  should  be  interrupted 
for  a  time  when  the  solid  will  dissolve  again.  The  chlorination  mixture 
is  allowed  to  stand,  and  is  poured  off  from  the  iron  sludge.  The  mixture 
is  rectified  by  means  of  a  fractionating  column.  Approximately,  the 
following  fractions  will  be  obtained  : — 


B.P. 

0/ 

/o 

Composition. 

79°- 

-81° 

3 

Benzene. 

81°- 

-125° 

10 

Benzene  and  chlor-benzene. 

126°- 

-133° 

85 

Chlor-benzene. 

133° 

-180° 

5 

Chlor-benzene  and  dichlor-benzene. 

5 

Resinous  matter  and  loss. 

THE  LINKING  OF  HALOGEN  TO  CARBON 


343 


The  fraction  126° — 133°  is  redistilled  through  the  column,  and  the 
fraction  131°— 132°  collected. 

C6H6  +  Cl2  ->  C6H5C1  +  HC1. 

Yield.— 90%  theoretical  (130  gms.).    Colourless  liquid  ;   B.P.  132°  ; 
D.(»  1-1284.    (B.,  11,  117  ;  26,  1053.) 
Preparation  343. — j9-Bromophenol. 

OH<^       ^>Br.        C6H6OBr.  174. 

100  c.cs.  of  carbon  disulphide  and  100  gms.  of  phenol  are  placed  in  a 
round-bottomed  flask  fitted  with  a  mechanical  agitator,  and  to  which 
is  attached  a  reflux  condenser  and  a  dropping-funnel  through  a  rubber 
stopper.  170  gms.  of  bromine  (54-6  c.cs.)  dissolved  in  50  c.cs.  of  carbon 
disulphide  are  placed  in  the  dropping-funnel.  The  flask  is  cooled  below 
5°  in  a  freezing  mixture,  and  after  starting  the  agitation  the  bromine  is 
slowly  run  in,  the  addition  requiring  about  2  hours.  The  mixture  is 
distilled  to  remove  the  carbon  disulphide.  The  residue  is  distilled  in 
vacuo,  using  a  Claisen  flask  and  a  good  fractionating  column.  The 
fraction  145° — 150°  at  25 — 30  mms.  is  collected,  and  on  cooling  sets  to  a 
solid  white  mass,  which  may  be  dried  by  pressing. 

OH<^  Br2  ->  OH<^  ^>Br. 

F^R— 80— 84%  theoretical  (145—155  gms.).    M.P.  63°— 64°. 
Note. — The  jobromophenol  should  not  be  allowed  to  come  in  contact 
with  the  stopper. 

(A.,  137,  200;  B.,  7,  1176;   "Organic  Syntheses,"  Vol.  I.,  Roger 
Adams,  and  others.) 
Preparation  344. — Benzal  Chloride  (Phenyl-dichlor-methan). 

<^       ^>CHC12.       C7H6C12.  161. 

445  gms.  toluene  and  10  gms.  phosphorus  pentachloride  are  heated  to 
boiling  in  a  litre  flask  provided  with  a  reflux  and  agitator.  Dry  chlorine 
is  passed  in  through  the  liquid  until  the  increase  in  weight  is  355  gms. 
The  chlorination  is  facilitated  by  bright  sunlight,  or  by  ultra-violet  light. 
The  chlorination  mixture  is  then  fractionally  distilled  and  the  fraction 
between  160° — 225°  collected.  This  fraction  is  further  fractionated, 
and  the  fraction  between  200° — 210°  collected  and  purified  by  distillation. 

The  impurities  present  after  chlorination  are  unchanged  toluene, 
benzyl-chloride  and  benzo-trichloride. 

^>CH3  +  2C12  ->  <^       ^>CHC12  +  2HC1. 

Yield.— 85%  theoretical  (660  gms.).  Colourless  liquid  ;  B.P.  206°  ; 
D.  1-2557.    (A.,  116,  336  :  146,  322  ;  139,  318.) 


344 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  345 —Benzyl  Chloride  (Phenyl-chlor-methan). 

C6H5.CH2.C1.       C7H7C1.  126-5. 

50  gms.  of  toluene  are  placed  in  a  tared  retort  (see  Fig.  52),  the  tubulus 
of  which  is  sloped  upwards  and  connected  to  a  water  reflux  condenser 
carrying  a  straight  calcium  chloride  tube  at  the  end.  2  gms.  phosphorus 
pentachloride  or  phosphorus  trichloride  to  act  as  chlorine  carrier  are  also 
placed  in  the  retort.  The  toluene  is  boiled  and  a  stream  of  dry  chlorine  is 
led  through  the  liquid  by  a  delivery  tube  fixed  by  a  cork  (an  ordinary 
cork,  previously  soaked  in  melted  paraffin  wax  should  be  used)  in  the  neck 
of  the  retort.  The  retort  is  weighed  periodically,  and  the  stream  of 
chlorine  continued  until  an  increase  in  weight  of  18-5  gms.  takes  place. 
The  product  is  distilled,  the  fraction  165° — 185°  being  collected  ;  this  is 


Fig.  52. 


redistilled,  collecting  the  fraction  176° — 180°,  which  is  practically  pure 
benzyl  chloride. 

C6H5.CH3  +  Cl2       C6H5CH2C1  +  HC1. 

Yield.— 60%  theoretical  (40  gms.).    B.P.  176°.    (A,  1853,  88,  129  ; 
B.,  18,  606  ;  A,  272,  149.) 
Preparation  346. — j>Nitrobenzyl  Bromide. 

N02.C6H4.CH2Br.       C7H602NBr.  216. 

Method  I. — 5  gms.  pure  ^-nitrotoluene,  2  c.cs.  of  bromine,  and  a 
crystal  of  iodine  are  placed  in  a  sealed  tube.  The  tube  is  placed  in  a 
bomb  furnace  and  gradually  heated  up  during  40  minutes  to  130°,  at 
which  temperature  it  is  maintained  for  160  minutes.  After  cooling,  the 
tube  is  opened  and  the  product  extracted  with  about  60  c.cs.  of  hot 
alcohol.  From  the  resulting  solution  crystals  separate  on  cooling,  which 
are  filtered  off  ;  a  second  crop  is  obtained  after  concentrating  and  cooling 


THE  LINKING  OF  HALOGEN  TO  CARBON 


345 


the  mother  liquor.    Water  is  added  to  the  final  mother  liquor  to  precipitate 
a  small  quantity  of  the  nitrobenzyl  bromide,  which  is  filtered  off,  dried, 
and  purified  by  recrystallisation  from  petroleum  ether.    The  first  and 
second  crops  should  be  washed  with  cold  petroleum  ether. 
Yield. — 75%  theoretical  (6  gms.). 

Method  II. — 10  gms.  of  ^-nitrotoluene  dissolved  in  100  c.cs.  of  carbon- 
tetrachloride  and  a  crystal  of  iodine  are  placed  in  a  silica  flask  provided 
with  a  reflux  condenser.  The  solution  is  covered  with  a  layer  of  water 
(about  50  c.cs.)  and  heated  to  gentle  boiling,  while  situated  about  15  cms. 
from  a  mercury  vapour  lamp.  A  solution  of  15  gms.  bromine  in  50  c.cs. 
carbon  tetrachloride  is  then  run  in  drop  by  drop  from  a  dropping-funnel 
at  the  top  of  the  condenser.  When  all  the  bromine  is  in,  boiling  is  con- 
tinued until  the  solution  becomes  almost  colourless.  The  contents  of  the 
flask  are  cooled,  transferred  to  a  separating  funnel,  and  the  lower  carbon 
tetrachloride  layer  run  into  a  distilling  flask.  Carbon  tetrachloride  is 
distilled  off  over  a  water  bath,  and  the  residue  of  ^-nitrobenzyl  bromide 
reCrystallised  from  alcohol  or  petroleum  ether. 

N02.C6H4CH3  +  Br2  ->  N02C6H4CH2Br  +  HBr. 

Yield.— 80%  theoretical  (12-6  gms.).  Needles  ;  M.P.  99°— 100°.  (See 
also  Am.  Soc,  40,  406.) 

Preparation  347. — Tetrabrom-diphenylamine  (2.4,2. 4-Tetra-brom-l- 
l'-diphenylamine). 


Br.f    YBr     Brf  )Br 

ClaH7NBr2.  485. 

4  gms.  (1  mol.)  of  finely  powdered  diphenylamine  are  agitated  with  a 
sufficient  quantity  of  cold  glacial  acetic  acid  to  dissolve  it.  The  solution 
is  stirred  while  5  c.cs.  (4  mols.)  of  bromine  dissolved  in  50  c.cs.  glacial 
acetic  acid  are  slowly  run  in.  The  tetrabrom-diphenylamine  formed 
separates  as  a  precipitate,  which  is  filtered  off  and  recrystallised  from 
alcohol. 

(C6H5)2NH  +  4Br2  ->  (C6H3Br2)2NH  +  4HBr. 

Yield. — Theoretical  (12  gms.).  Colourless  needles  ;  M.P.  182°.  (A., 
132,  166  ;  B.,  8,  825.) 

Preparation  348. — m  -  Bromobenzoic  Acid  (1  -  Carboxyl  -  3  -  brom- 
benzene). 

Br 

<^       ^>COOH.        C7H502Br.  201. 

6  gms.  (1  mol.)  of  benzoic  acid,  8  gms.  (1  mol.)  of  bromine,  and  40  gms. 
of  water  are  heated  together  in  a  thick-walled  sealed  tube  to  about 
140° — -150°  in  the  usual  type  of  furnace  for  9  hours.  After  cooling,  the 
tube  is  opened  with  the  usual  precautions,  and  the  colourless  crystals  of 
bromobenzoic  acid  washed  out,  filtered,  and  boiled  with  100  c.cs.  of  water 


346 


SYSTEMATIC  ORGANIC  CHEMISTRY 


in  a  basin  for  1  hour  to  remove  unchanged  benzoic  acid.  The  residual 
bromobenzoic  acid  is  then  recrystallised  twice  from  hot  water. 

C6H5.COOH  +  Br2  =  C6HJ.Br,CO.OH  -f  HBr. 

Yield—  80%  theoretical  (8  gms.).  .  Colourless  needles  ;  soluble  in  hot 
water  ;  M.P.  155°.    (A.,  149,  131.) 

Preparation  349. — Dibrom-succinic  Acid  (2.3-Dibrom-butan-diacid). 

CHBrCOOH 

C4H404Br2.  276. 

CHBrCOOH 

12  gms.  (1  mol.)  of  succinic  acid,  32  gms.  (1  mol.)  of  bromine,  and  12  gms. 
of  water  are  heated  in  a  sealed  tube  for  6  hours  at  170°  (see  p.  38). 
The  tube  is  then  opened  in  the  usual  way.  The  greyish-white  mass  with 
which  the  tube  is  now  filled  is  recrystallised  from  boiling  water,  with  the 
addition  of  a  little  animal  charcoal. 

CH2.COOH  CHBrCOOH 
j  +  2Br2  =    j  +  2HBr. 

CH2.COOH  CHBrCOOH. 

Yield. — Theoretical  (27  gms.).  Colourless  glistening  crystals  ;  soluble 
in  hot  water,  soluble  in  alcohol  and  in  ether  ;  decomposes  at  200°  with 
formation  of  hydrobromic  acid  and  brom-maleic  acid.  (A.,  117,  120  ; 
A.  Spl.,  1,  351  ;  BL,  18,  168.) 

Preparation  350. — a-Bromonaphthalene. 


Br 


116  gms.  of  naphthalene  (flakes)  and  125  c.cs.  of  water  are  placed  in  a 
pot  fitted  with  a  good  mechanical  agitator  and  heated  to  40°- — 50°. 
145  gms.  (45  c.cs.)  of  bromine  are  then  gradually  dropped  in  from  a 
dropping- funnel  dipping  to  the  bottom  of  the  pot,  at  such  a  rate  that  the 
temperature  is  maintained  at  40° — 50°.  The  addition  takes  8 — 9  hours. 
After  all  the  bromine  has  been  added,  stirring  is  continued  until  the 
colour  has  practically  disappeared.  The  mixture  is  allowed  to  cool,  and 
a  heavy  oil  separates.  The  oil  is  steam-distilled  on  an  oil  bath  at 
145° — 150°,  this  process  removing  the  hydrobromic  acid  and  some 
unchanged  naphthalene.  The  oil  is  distilled  in  vacuo,  the  fraction 
132°— 133°  at  12  mms.  (145°— 148°  at  20  mms.)  being  collected.  The 
lower  fractions  contain  naphthalene,  and  the  higher,  1.4-dibromo- 
naphthalene. 

C10H8  +  Br2  =  C10H7Br  +  HBr. 

Yield.— 55— 60%  theoretical  (100—110  gms.).  (A,  135,  40  ;  147,  166  ; 
"  Organic  Synthesis,"  Vol.  I.,  Roger  Adams,  and  others.) 


THE  LINKING  OF  HALOGEN  TO  CARBON 


347 


Pkeparation  351 . — Tribrom-s-xylenol. 

(CH3)2C6Br3(OH).       C8H7OBr3.  359. 

A  few  gms.  of  xylenol  are  placed  in  a  large  test  tube,  or  small  beaker, 
and  covered  with  about  20  times  their  weight  of  water.  Bromine  is 
gradually  added  drop  by  drop  until  an  excess  is  indicated  by  a  reddish- 
brown  colour  which  does  not  disappear.  Sulphur  dioxide,  either  as 
aqueous  solution  or  gas,  is  added  until  the  excess  of  bromine  is  removed. 
The  precipitate  is  filtered  off,  washed  with  water,  and  recrystallised  from 
alcohol. 

CH  =  C(OH)  C.Br  =  C.OH 

CH3C^          ^CH  +  3Br2        CH3C<^  ^-Br  +  3HBr. 

CH — C.CH3  XCBr  C.CH3 

Yield.— 90%  theoretical.  Fine  needles  ;  M.P.  166°.  (B.,  18,  2679  ; 
A.,  281,  122.) 

Preparation  352. — Tribromophenol  (1  -  Hydroxy  -  2.4.6  -  tribromo- 
benzene). 

C6H2(OH)Br3.       C6H3OBr3.  331. 

5  gms.  (1  mol.)  of  phenol  are  dissolved  in  100  c.cs.  of  water,  and  to  the 
cold  solution  8-3  c.cs.  (3  mols.)  of  bromine  in  aqueous  solution  are  added. 
The  precipitate,  which  is  almost  insoluble  in  water,  is  filtered  off,  washed 
with  water,  and  recrystallised  from  dilute  alcohol. 

C6H5(OH)  +  3Br2  ->  C6H2Br3(OH)  +  3HBr. 

Yield.— Theoretical  (17  gms.)    Colourless  needles  ;  M.P.  95°.    (A.,  43, 
212  ;  137,  208.) 
Preparation  353 . — /y-Brom-dimethylaniline. 

C6H4BrN(CH3)2.       C8HieNBr.  200. 

10  gms.  dimethylaniline  are  dissolved  in  glacial  acetic  acid,  and  6-6  gms. 
bromine  dissolved  in  glacial  acetic  acid  gradually  added.  When  the 
solution  is  diluted  with  water,  the  ^-brom-dimethylaniline  is  precipitated, 
filtered  off,  and  recrystallised  from  alcohol. 


C6H5N(CH3)2  ->  CeH4Br.N(CH3) 


Yield.— Ahaost  theoretical  (16—17  gms.).    White  plates  ;  M.P.  55°. 
(B.,  8,  715.) 
Preparation  354. — Benzoyl  Chloride. 

C6H5C0C1.       C7H50C1.  140-5. 

Dry  chlorine  is  led  into  cold  benzaldehyde  (for  apparatus  see  p.  344). 
The  chlorine  is  easily  absorbed  with  evolution  of  heat,  torrents  of  hydro- 
chloric acid  being  given  off.  When  the  reaction  has  moderated  some- 
what, heat  is  applied  in  order  to  keep  the  liquid  boiling  briskly,  the 
stream  of  chlorine  being  continued  until  the  evolution  of  hydrochloric 
acid  ceases.    The  excess  chlorine  is  removed  by  passing  a  stream  of  dry 


348  SYSTEMATIC  ORGANIC  CHEMISTRY 


air  or  carbon  dioxide  through  the  apparatus.  The  product  is  then 
distilled. 


XH  \C1. 


I  teld. — Almost  theoretical.    Colourless,  fuming  liquid,  with  irritating 
smell ;  B.P.  198°  ;  D.  "  1-214.    (A.,  3,  1262.)  * 
Preparation  355. — Chloral, 

CCl3CHO       C2H0C13.  147-5. 

100  c.cs.  absolute  alcohol  are  placed  in  a  retort,  with  the  side  tube  on 
the  slant  and  attached  to  a  reflux,  and  which  can  be  cooled.  A  current 
of  dry  chlorine  is  passed  into  the  alcohol,  the  temperature  being  kept 
below  10°.  The  gas  is  quickly  absorbed  at  first,  but  the  absorption 
slackens  off.  The  contents  of  the  retort  are  heated  to  60°,  while  chlorine 
is  still  passed,  as  long  as  it  is  absorbed.  The  liquid  is  then  boiled 
gently  and  cooled— its  specific  gravity  should  now  be  1-400.  An  equal 
volume  of  cone,  sulphuric  acid  is  now  cautiously  added,  ethyl  chloride 
and  hydrochloric  acid  being  evolved.  The  mixture  is  distilled  from  a 
water  bath.  The  distillate  is  neutralised  with  chalk  and  again  distilled 
and  finally  fractionated,  the  fraction  boiling  at  93°— 96°  being  retained.' 

CI  CI 
CH3CH2OH  ->  CH3CHO  ->  CCI3CHO. 

Colourless  liquid ;  characteristic  odour ;  B.P.  94-5°.  (Z  Ch  1870 
172;  A.,  279,  293.)  K  '    .  ' 

When  chloral  is  mixed  with  J  its  weight  of  water,  the  mixture  gradually 
solidifies  to  a  crystalline  mass  of  chloral  hydrate. 

CCI3CHO  +  H20  ->  CC13CH(0H)2. 

Colourless  crystals;    M.P.  57°;    B.P.  97°.  with  decomposition:  is 
converted  into  chloral  by  sulphuric  acid.    (Z.,  1870,  172,  351.) 
Preparation  356.— Mono-chloracetic  Acid. 

CH2Cl.COOH.       C2H302C1.  94-5. 

100  grns.  glacial  acetic  acid  and  10  gms.  of  sulphur  are  placed  in  a  small 
flask  and  the  whole  weighed.  The  flask  is  fitted  with  a  two-holed  cork, 
one  hole  being  fitted  with  an  adapter,  to  which  is  attached  a  reflux  con- 
denser, while  the  other  is  fitted  with  a  delivery  tube  reaching  down  into 
the  acid.  The  flask  is  heated  on  a  boiling  water  bath,  and  a  steady 
current  of  chlorme  passed  into  the  acid,  until  (about  6  hours)  a  gain 
m  weight  of  50  gms.  has  taken  place.  As  it  has  a  catalytic  accelerating 
effect  on  the  operation  it  is  important  to  place  the  apparatus  in  direct 
sunlight.  When  the  required  increase  has  taken  place,  the  liquid  is 
decanted  from  the  sulphur  into  a  distilling  flask  and  distilled  through  an 
air  condenser.  Acetyl  chloride,  sulphur  chloride  and  acetic  acid  come 
over  at  first.  The  fraction  150°— 190°  is  collected  separately  ;  this  yields 
crystals  of  mono-chloracetic  acid,  on  cooling  ;  the  liquid  is  drained  off 


THE  LINKING  OF  HALOGrEN  TO  CARBON 


349 


Tom  the  crystals,  the  latter  redistilled,  and  the  fraction  180° — 190° 
jollected. 

CIIa.COOII  +  Cl2       CH2Cl.COOH  +  HCL 

Yield. — 45—60%   theoretical  (75—100   gms.).    Colourless  crystals. 
tf.P.  62°— 63°;  B.P.  185°— 187°.    (Bl.  [3],  2,  145.) 
Preparation  357 . — Trichloraniline. 

Cl_ 

NH,^       ^>C1.       C6H4NC12.  196-5. 
Cl 

10  gms.  of  dry  aniline  are  dissolved  in  200  gms.  dry  carbon  tetrachloride, 
md  placed  in  a  flask  fitted  with  a  mechanical  agitator  (see  Fig.  37). 
Fhe  flask  is  surrounded  by  an  efficient  freezing  mixture,  so  that  the 
emperature  is  about  —  10°.  Through  one  of  the  side  tubes  is  passed 
Iry  chlorine  mixed  with  dry  carbon  dioxide  (equal  volumes).  A  white 
srystalline  deposit  of  trichloraniline  is  thrown  down,  but  if  the  tempera - 
ure  is  allowed  to  rise  or  the  materials  used  not  absolutely  dry,  the  product 
s  contaminated  with  aniline  black.  The  crystals  are  filtered  off  and 
ecrystallised  from  alcohol. 

_CI 

<^  )nh2  ->  ci<(  )nh, 

Cl 


Yield. — Almost  theoretical  (21  gms.).  White  needles;  M.P.  77-5°: 
3.P.  262°. 


CHAPTER  XXIII 


THE  LINKING  OF  HYDROGEN  TO  NITROGEN 

Amino  Compounds 

Reaction  CLXIX.  Action  of  Metals  on  Nitro  Compounds  in  Acid 
Solution. 

— N02  ->  NH2. 

The  metals  used  are  iron,  zinc,  tin  ;  and  the  acids,  hydrochloric,  sulphuric, 
and  in  some  cases  acetic.  As  a  rule,  the  best  temperature  for  the  reduction 
is  about  100°,  and  in  some  cases  the  nitro  compound  may  be  dissolved  in  a 
suitable  solvent.  In  all  cases,  good  mechanical  agitation  is  essential  to 
prevent  the  metal  settling  to  the  bottom  of  the  pot.  When  iron  is  used 
along  with  hydrochloric  acid,  the  acid  acts  as  a  catalyst,  and  very  little 
need  be  used  in  the  reaction  (see  note  under  aniline). 

The  amine  is  obtained  in  the  form  of  its  salt,  the  base  being  liberated 
by  caustic  soda.  The  amine,  if  volatile  in  steam,  is  separated  by  steam 
distillation  ;  solid  amines  are  separated  by  filtration.  Sometimes  the 
amine  may  be  extracted  with  ether,  but  before  this  is  done  the  metal 
should  first  be  removed. 

Where  zinc  and  tin  are  used,  double  salts  of  the  general  formula, 
R.NH2.HC1.MC12,  sometimes  separate  out  when  the  reductim  is  com- 
plete, e.g.,  chlor-anilines.  These  salts  may  be  decomposed  my  excess 
of  caustic  soda,  and  the  base  isolated  as  before. 

The  reaction  is  applicable  to  both  aliphatic  and  aromatic  nitro  com- 
pounds. 

Preparation  358. — Aniline  (Amino-benzene). 

C6H5NH2.       C6H7N.  93. 

I 

This  compound  should  be  made  in  a  closed  pot,  to  which  very  efficient 
agitation  is  fixed,  and  attached  to  a  reflux  condenser,  as  shown  in  Fig.  36. 
The  metal  used  in  this  reduction  is  iron,  and  should  be  in  as  fine  a  state 
as  possible.  * 

60  c.cs.  of  water  and  120  gms.  of  iron  powder,  are  placed  in  the  reduction 
pot,  agitation  being  maintained  during  the  addition.  The  pot  is  then 
heated  to  90° — 95°,  and  10  c.cs.  cone,  hydrochloric  acid  (D.  1-18)  is  poured 
in  ;  100  gms.  nitrobenzene  are  then  added,  a  few  c.cs.  at  a  time.  The 
temperature  must  be  held  at  100°  C,  and  this  can  be  conveniently  done  by 
regulating  the  addition  of  the  nitrobenzene.  When  all  the  latter  has 
been  added,  the  reduction  is  continued  at  about  100°  C.  until  no  smell 
of  nitrobenzene  remains,  or  until  a  sample  dissolves  completely  in 
hydrochloric  acid. 

350 


THE  LINKING  OF  HYDROGEN  TO  NITROGEN  351 


If  the  agitation  is  not  powerful  enough  to  carry  through  this  process, 
the  following  may  be  adopted  :  100  gms.  of  nitrobenzol  and  60  c.cs.  water 
and  10  c.cs.  of  cone,  hydrochloric  acid  (D.  1-18)  are  heated  in  the  pot  up 
to  95°  C.  1 20  gms.  iron  powder  is  then  added  carefully,  the  temperature 
being  maintained  at  about  100°  C.  After  all  the  iron  has  been  added, 
the  temperature  is  maintained  at  100°  C.  by  external  heat,  and  agitation 
continued  until  all  the  nitrobenzene  has  been  reduced. 

Steam  Distillation. — If  direct  steam  can  be  led  into  the  reduction  pot, 
this  process  is  simplified,  for,  by  merely  altering  the  condenser  to  the 
usual  sloping  position,  the  aniline  can  be  distilled  off.  If  no  direct  steam 
can  be  lead  into  the  reduction  pot,  the  contents,  after  the  reduction  is 
finished,  are  poured  into  a  large  round-bottomed  flask,  and  steam  from  a 
steam  generator  led  into  it,  the  products  of  vaporisation  being  condensed 
in  the  usual  way  (see  Fig.  14). 

Separation. — The  condensate  is  poured  into  a  separating  funnel  and 
allowed  to  stand  until  separation  into  two  layers  is  complete.  This 
may  be  assisted  by  applying  heat  or  by  adding  salt.  The  aniline  is  then 
poured  off  and  dried  over  solid  caustic  soda  and  then  distilled. 

CeH5N02  +  3Fe  +  6HC1  ->  C6H5NH2  +  3FeCl2  +  2H20. 

Yield.— 95%  theoretical  (70  gms.).  B.P.  184°  ;  D.  1-026  ;  important 
intermediate  for  dyestuffs. 

Note. — The  quantity  of  hydrochloric  acid  used  in  an  acid  reduction 
where  iron  is  employed  is  only  about  ^  of  the  quantity  required  by 
theory.  This  is  explained  by  the  fact  that  the  hydrochloric  acid  acts  as  a 
catalytic  agent. 

(1)  Fe  -f  2HC1  ->  FeCl2  +  H2. 

(2)  FeCl2  +  2H90  ->  Fe(OH)2  +  2HC1. 

(3)  2.RNH2.HC1  +  Fe  ->  2.ENH2  +  FeCl2  +  H2. 

Equation  (1)  shows  the  first  reaction  between  Fe  and  HC1. 

Equation  (2)  shows  the  formation  of  Fe(OH)2,  which  is  itself  a  powerful 
reducing  agent.  It  is  possible  to  reduce  nitrobenzene  to  aniline  with 
alkaline  ferrous  sulphate  (Fe(OH)2). 

Equation  (3)  shows  the  regeneration  of  FeCl2  and  H  by  the  action  of 
the  metal  on  the  hydrochloride.  It  is  possible  to  reduce  nitrobenzene 
with  a  non-substituted  ammonium  salt,  e.g.,  ammonium  chloride  and  a 
metal  (D.R.P.,  89978).    (A.,  55,  200  ;  B.,  19,  903  ;  13,  1298  ;  19,  2916.) 

Peeparation  359. — o-  and  £>-Toluidine  (1*2  and  1'4-Methyl  amino 
benzene). 

eH3<^       \andCH3/      ^>NH2.       C7H9N.  107. 

The  reduction  of  nitrotoluene  is  similar  to  that  given  for  nitrobenzene 
under  aniline  (p.  350).  The  steam  distillation  is  similar,  the  ortho-  and 
??ara-compounds  formed  in  the  reduction  passing  over. 

Separation  cfo-  and  p-Toluidine  (a).— The  oil  is  separated  from  the  water 
and  ice  and  salt  added  and  the  mixture  stirred.    A  whitish-yellow 


352 


SYSTEMATIC  ORGANIC  CHEMISTRY 


crystalline  compound  will  appear,  which  is  the  hydrate  of  the  jo-compound . 
This  is  filtered  off  through  an  ice  filter,  and  the  hydrate  well  pressed  to 
remove  any  adhering  oily  or^o-compound.  The  or^o-compound  passes 
through  the  filter  along  with  the  water,  and  is  separated,  as  in  the  separa- 
tion of  aniline.  The  £>ara-compound  is  recrystallised  from  alcohol. 
(J.  S.  C.  I.,  27,  258.) 

Separation  of  Pure  o-Toluidine  (b). — The  mixture  containing  the  o-  and 
^-compounds  is  dissolved  in  hydrochloric  acid  until  slightly  acid  to  Congo 
Red,  and  water  added  until  the  solution  is  saturated  at  ordinary  tempera- 
ture. Saturated  aqueous  sodium  ferrocyanide  is  then  gradually  added 
with  shaking,  when  the  greenish-white  needles  of  o-toluidine  hydro- 
ferrocyanide  come  down.  The  solution,  after  precipitation  is  complete, 
is  still  slightly  acid.  The  o-compound  is  filtered  off,  washed  with  a 
little  water,  and  a  very  little  dilute  hydrochloric  acid.  It  is  dried, 
and  the  base  obtained  from  it  by  decomposing  with  caustic  soda  and 
extraction  with  ether.  After  drying  the  ethereal  solution  with  potassium 
carbonate,  and  removing  the  ether,  the  base  distils  at  198°. 

NQ2  NH2 
CH3<^       ^    >  CH3<^  ^) 

Yield— 90— 95%  theoretical  (total  o  and  p).  b,  B.P.  198° ;  D.  1-003  ; 
p,  M.P.  45°  ;  B.P.  200°  ;  D.  1-046  ;  important  intermediate  for  dves. 
(J.  C.  S.,  121,  1294.) 

Pkeparation  360. — a-Naphthylamine. 

NH2 

'[      )      j       C10H9N.  143. 

The  reduction  is  similar  to  that  of  nitrobenzene  (Preparation  358),  but 
no  condenser  need  be  used  in  this  case.  120  gms.  iron  powder  and 
60  c.cs.  water  are  placed  in  the  reduction  pot,  and  the  temperature 
raised  to  95°.  10  c.cs.  of  cone,  hydrochloric  acid  are  then  poured 
in  and  100  gms.  a-nitronaphthalene  added  gradually.  The  reduction 
is  continued  until  a  sample  is  completely  soluble  in  hydrochloric  acid. 

Separation. — The  steam  distillation  is  carried  out  as  in  Preparation  358, 
using  in  this  case  superheated  steam.  A  convenient  apparatus  for 
producing  superheated  steam  is  shown  in  Fig.  15.  The  naphthylamine 
is  then  filtered  off  and  crystallised  from  benzene  or  toluene. 

Yield.— 80— 85%  theoretical  (65—70  gms.).  M.P.  51°  ;  B.P.  300°  ; 
D.  1-23.  A  small  percentage  of  ^-naphthylamine  is  formed  in  the 
reduction.    (J.  pr.,  27,  140  ;  A.,  92,  401  ;  275,  217.) 

Preparation  361 . — m-Phenylene-Diamine   (Hydrochloride) . 
NH  2 

<^       ^>NH2.HC1.       C6H9N2CJ.  144-5. 

This  process  is  carried  out  in  the  usual  reduction  pot  with  reflux  attached 
(see  Fig.  36). 


THE  LINKING  OF  HYDROGEN  TO  NITROGEN 


353 


150  c.cs.  water  are  placed  in  the  reduction  pot  and  heated  up  to  95°  C, 
and  100  gms.  m-dinitrobenzene  (M.P.  91°  C.)  are  then  added.  10  c.cs. 
of  cone,  hydrochloric  acid,  and  about  120  gms.  of  fine  iron  powder  are 
added  gradually,  care  being  taken  that  the  contents  do  not  froth  over. 
This  process  is  carried  on  until  the  solution  loses  its  yellow  colour,  as  may 
be  shown  by  spotting  on  filter  paper.  A  solution  of  sodium  carbonate  is 
then  added  until  an  alkaline  reaction  is  obtained.  It  is  boiled  and  filtered 
from  the  iron  residue.  The  iron  residue  is  again  boiled  with  water  and 
filtered.  The  combined  filtrates  are  evaporated  to  a  convenient  bulk  and 
cone,  hydrochloric  acid  added  to  precipitate  the  hydrochloride.  This  is 
allowed  to  cool,  and  is  filtered  and  dried. 


NO,  NH2 


Yield.— 90%  theoretical  (77  gms.).    M.P.  61°  ;  B.P.  283°.    (J.,  1861, 
512  ;  1863,  422  ;  Z.  Ch,  1865,  51.) 
Preparation  362. — /9-Phenylene-Diamine. 

NH2<^       ^>NH2.       C6H8N2.  108. 

The  process  is  similar  to  that  used  for  making  the  meto-compound. 
In  this  case,  however,  j9-nitraniline  (M.P.  148°)  is  added  to  the 
mixture  of  iron  powder,  water,  and  acid.  The  following  quantities  are 
used  : — 

100  gms.  iron  powder  ;  5  c.cs.  cone,  hydrochloric  acid  ;  100  c.cs.  water. 

These  are  heated  to  95°  0.  and  100  gms.  ^-nitraniline  gradually  added. 
Cooling  may  have  to  be  applied  to  regulate  the  action. 

The  reduction  is  continued  as  in  Preparation  361  until  the  liquid  loses  its 
yellow  colour. 

Sodium  carbonate  is  added,  as  before,  until  alkaline.  After  the  iron 
residue  is  filtered  of!  the  filtrate  is  concentrated  until  the  base  crystallises. 

NQ2<(       )NH2  ->  NH2(  )NH2. 

Yield.— 90%  theoretical  (57  gms.).    M.P.  147°  ;  B.P.  267°.    (J.,  1863, 
422  ;  B.,  7,  871  ;  28,  250.) 
Preparation  363.— Metanilic  Acid  (Aniline  m-sulphonic  acid). 

SQ3H. 

NH2/       y  C6H703NS.  173. 

Nitrobenzene  m-sulphonic  acid  is  prepared  as  on  p.  306.  The  reduction 
is  carried  out,  using  iron  powder,  as  in  H  acid  (p.  307).  After  the  reduc- 
tion is  neutralised  and  filtered,  the  filtrate  is  concentrated  to  about 
600  c.cs.  Hydrochloric  acid  is  added  until  an  acid  reaction  to  Congo  is 
obtained.  The  metanilic  acid  then  crystallises  out.  The  separation 
may  be  assisted  by  adding  common  salt. 

Yield. — 80%  theoretical.  (Crystallises  with  |H20  of  crystallisation  ; 
intermediate  for  dyestuffs.    (Z.  a.,  9,  686.) 


S.O.C. 


A  A 


354  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  364—  Diamido  Stilbene  Disulphonic  Acid. 

SQ3H  SO3H 
NH2<^       ^>CH  =  CH<^       ^>NH2.       C14H1406N2S2.  370. 

The  sodium  salt  of  the  dinitro  acid  from  Preparation  294  is  dissolved  in 
300  c.cs.  hot  water,  and  hydrochloric  acid  is  added  to  neutralise  any  free 
sodium  carbonate.  The  solution  is  run  on  to  200  gms.  of  iron  turnings, 
which  have  been  previously  etched  by  standing  in  20  c.cs.  of  40%  acetic 
acid.    The  reduction  proceeds  in  the  normal  way. 

The  clear  solution  is  made  strongly  acid  to  Congo  with  hydrochloric 
acid,  and  the  diamido  stilbene  sulphonic  acid  separates  as  yellow  crystals. 
After  10  hours  it  is  filtered  of!  and  washed. 

Yield. — About  40%  (calculated  on  ^9-nitrotoluene).  Important  inter- 
mediate for  dyestuffs.    (B.,  30,  3100.) 

Preparation  365. — 4- Amino  m-Hydroxy  Benzoic  Acid. 
 OH 

COOH^       ^NH2.       C7H703N.  153. 

10  gms.  4-nitro-m-hydroxy  benzoic  acid  (see  p.  262)  and  200  c.cs.  cone, 
hydrochloric  acid  are  heated  on  a  water  bath,  and  30  gms.  of  tin  slowly 
added.  After  the  reaction  is  complete  the  double  tin  salt  separates  out, 
and  is  filtered.  The  precipitate  is  dissolved  in  200  c.cs.  of  warm  water 
and  hydrogen  sulphide  passed  until  all  the  tin  is  separated.  The  filtrate 
from  the  tin  is  concentrated  until  crystals  of  the  hydrochloride  begin  to 
separate.  When  cold,  the  hydrochloride  is  filtered,  dissolved  in  a  little 
water,  and  the  free  base  precipitated  by  the  addition  of  a  cone,  solution 
of  sodium  acetate.  It  is  filtered,  washed  with  water,  and  recrystallised 
from  hot  water  or  dilute  alcohol. 

COOH  COOH 
OH<^      ^NO,   ->   OH<^  \NH2. 

Yield.— 60%  theoretical  (5  gms.).  M.P.  115°— 116°.  (J.  C.  S.,  119, 
1429.) 

Preparation  366. — ^-Amino-acetanilide. 

NH2<^       ^>NH.COCH3.       C8H10ON2.  150. 

93  gms.  of  aniline  are  converted  into  acetanilide,  and  then  to  nitro- 
acetanilide,  as  shown  in  the  preparation  of  jo-nitraniline  (p.  268).  The 
moist  nitro-compound  is  then  added  in  small  portions  to  a  vessel  fitted 
with  good  agitation  (see  Fig.  36),  and  containing  125  gms.  iron  filings, 
8  c.cs.  40%  acetic  acid  and  500  c.cs.  water  heated  to  boiling.  Boiling  is 
continued  for  10  minutes  after  the  last  addition,  when  the  solution 
"  spotted  "  on  filter  paper  should  be  colourless.  The  liquid  is  then  cooled 
to  70°,  and  sodium  carbonate  is  added  until  the  reaction  is  alkaline.* 
The  precipitation  of  the  iron  is  completed  by  adding  the  minimum 

*  If  the  sodium  carbonate  is  added  at  100°  or  in  excess,  hydrolysis  of  the 
nitroacetanilide  takes  plac^. 


THE  LINKING  OF  HYDROGEN  TO  NITEOGEN  355 


quantity  of  ammonium  sulphide  until  a  drop  on  filter  paper  gives  no 
coloration  with  sodium  sulphide.  The  whole  is  then  filtered,  and  the 
filtrate  evaporated  to  400  c.cs.,  when,  on  cooling,  the  amino -ace tanilide 
crystallises  in  long  needles.  A  further  crop  of  crystals  may  be  obtained 
by  evaporating  the  mother  liquor. 

N02<^       ^>NH.COCH3  ->  NH2/  ^>NH.CO.CH3. 

Yield.— 55%  theoretical  (80—90  gms.).    M.P.  162-5°  ;  on  hydrolysis 
gives  ^-phenylene  diamine.    (B.,  17,  343  ;  A.,  293,  373.) 
Preparation  367— ^-Phenetidine  (l.Ethoxy-4.amino-benzene). 

C2H50<^       ^>NH2.       C8HnON.  137. 

1.  ip-Nitrophenetole. — 14  gms.  ^-nitrophenol  are  dissolved  in  40  gms. 
of  10%  caustic  soda  solution,  and  the  solution  is  placed  in  an  enamel-lined 
autoclave  fitted  with  a  stirrer.  7  gms.  ethyl  chloride  are  introduced, 
and  the  mixture  heated  for  7 — 8  hours  at  90° — 100°.  After  cooling, 
the  ^-nitrophenetole  is  filtered  oil  and  washed  with  dilute  caustic  soda  to 
remove  unchanged  nitrophenol,  and  then  with  water. 

2.  ip-Phenetidine. — 10  gms.  ;p-nitrophenetole,  20  c.c.  water  and  1  c.c. 
cone,  hydrochloric  acid  are  placed  in  a  flask  or  a  sulphonating  pot  fitted 
with  a  good  mechanical  agitator  (see  Fig.  36).  The  temperature  is 
raised  to  60°,  and  iron  filings  (10  gms.)  are  gradually  introduced  over 
3 — 4  hours.  When  all  the  iron  has  been  added  the  temperature  is  raised 
to  90°,  where  it  is  maintained  until  the  reduction  is  complete.  The 
supernatant  aqueous  liquor  is  poured  or  siphoned  off,  and  the  sludge  is 
steam-distilled  with  superheated  steam  at  160° — 180°,  when  the  jo-phene- 
tidine  passes  over,  and  is  separated  from  the  aqueous  distillate  by 
extraction  with  ether,  and  purified  by  distillation. 

HO^       \NOa  ->  C2H50<^  ^>N02  ->  C2H50<^  ^>NH2. 

Liquid  ;  B.P.  244°.    (Am.  Soc.;  1,  272  ;  B.,  22,  1782.) 

Reaction  GLXX.  Action  of  Metals  on  Nitro  Compounds  in  Alkaline 
Solution. — The  metal  usually  employed  is  zinc,  although  iron  powder  can 
be  used  in  some  cases.  The  reaction  is  usually  carried  out  in  caustic 
soda  solution, 

Zn  +  2NaOH  — >  Zn(ONa)2  -f  H2, 
and  the  reaction  takes  place  in  several  stages. 


RN02  R — Nx  R.N  =  N.R 

+  6H   ->  i   >0    azoxy— or  || 

RN02  R— N'/  O 

R— Nx  R — N 

i  >  O  +  2H  ->         ||  azo— 

R— N/  R  .  N 

R — N  R.NH 

||  +  2H  ->       |  hydrazo— 

R  .  N  R.NH 


A  slight  excess  of  metal  is  required,  and  each  stage  can  be  isolated  by 


356 


SYSTEMATIC  ORGANIC  CHEMISTRY 


using  the  required  amount  of  metal,  e.g.,  §  for  the  azoxy  stage,  f  for  the 
azo  stage. 

Good  agitation  is  essential,  and  a  solvent  may  be  used  in  some  cases. 
This,  however,  is  not  always  necessary  if  the  agitation  is  efficient.  The 
compounds  are  separated  by  dissolving  out  the  zinc  with  ice-cold  hydro- 
chloric acid.  The  hydrazo  compounds,  when  heated  with  mineral  acids, 
undergo  a  rearrangement  (benzidine  conversion). 

K.NH — NH.R  — >  NH2K— K.NH2. 

the  NH2  groups  taking  the  ^-position,  although  a  certain  amount  of  o-p- 
ompound  is  formed, 

NH2   

<^__^>NH— NH<(  ^>    ->   )>NH2f 

as  well  as  o-  and  ^-semidines  (see  p.  155). 

The  sulphates  of  these  last  compounds  are  soluble  in  water,  and  they 
can,  therefore,  be  separated  from  the  ^p-^-compounds  by  means  of  sodium 
sulphate  or  sulphuric  acid. 

Preparation  368. — Benzidine  (4.4y-Diamino-diphenyl). 


H2N^~  <       \nH2.       C^H^N,.  184. 


1.  Hydrazobenzene.-— 100  gms.  nitrobenzene,  100  gms.  of  cone,  caustic 
soda  (30%  solution)  and  100  gms.  water  are  placed  in  the  reduction  pan 
(see  Fig.  36)  and  heated  to  95°  Q'.,  and  all  external  heat  cut  off.  Zinc 
dust  of  good  quality  (over  85%  metallic  zinc)  is  then  added,  a  few  gms. 
at  a  time.  The  heat  of  reaction  will  raise  the  temperature  to  100°  C, 
and  when  it  cools  to  98°  C.  a  few  more  gms.  of  zinc  dust  are  added,  the 
temperature  being  allowed  to  drop  to  98°  C.  before  any  further  addition  of 
zinc  is  made. 

During  the  course  of  the  reduction  small  samples  are  abstracted  by 
means  of  a  rod.  It  will  be  noticed  that  at  first  a  yellowish-red  crystalline 
solid  is  formed  on  the  rod,  then  a  red  crystalline  solid,  and  ultimately  all 
trace  of  red  disappears  and  a  lemon-yellow  crystalline  solid  is  formed. 
When  this  stage  is  reached  further  addition  of  zinc  is  stopped,  and  the 
whole  is  allowed  to  run  for  \  hour,  external  heat  being  applied.  In  all 
about  160  gms.  of  zinc  dust  will  be  necessary,  the  amount,  of  course, 
depending  on  the  metallic  content  of  the  dust. 

The  whole  is  quickly  cooled  by  adding  a  large  bulk  of  cold  water  to 
the  reduction  pot,  agitation  being  maintained. 

When  cooled  to  30°,  the  contents  of  the  pot  are  poured  into  a  large 
enamelled  bucket.  A  large  quantity  of  ice  is  added,  and  cone,  hydro- 
chloric acid  is  poured  in,  with  stirring.  The  temperature  should  not  rise 
above  5°  C.  Acid  is  added  until  the  liquid  in  the  bucket  gives  an  acid 
reaction  to  Congo  paper.  The  hydrazobenzene  is  then  filtered  off  and 
washed  with  cold  water. 

2.  Benzidine. — It  is  then  removed  to  a  basin  where  it  is  boiled  up  slowly  \ 
with  500  c.cs.  water  and  120  c.cs.  cone,  hydrochloric  acid  and  filtered  from 


THE  LINKING  OF  HYDROGEN  TO  NITROGEN  357 


zinc  residue.  A  saturated  solution  of  sodium  sulphate  is  then  added  until 
the  benzidine  sulphate  is  completely  precipitated  (test).  This  is  filtered  off 
and  is  well  washed  with  warm  water  until  free  of  acid.  The  moist  benzidine 
sulphate  is  removed,  heated  to  50°  C.  with  a  little  water,  and  caustic  soda 
solution  (30%)  added  with  stirring  until  the  liquid  is  just  alkaline  (test  with 
phenolphthalein).  When  cold,  the  free  base  is  filtered  off  and  dried  at 
50°  C.  It  may  be  crystallised  from  benzene  or  alcohol  or  from  hot  water 
(not  boiling). 

\  /N°2      H  \  /?\  \  A 


no,.  \  ~\nh 


Azoxy  Azo  Hydrazo 

(yellow -red)  (red)  (white) 

M.P.  36°.  M.P.  68°         M.P.  131° 

<^       ^NH- NH<^      ^>  C1H.H2N<^      ^>— <^  ^>NH2.HC1. 

H2S04  /  v       /  \ ,  NaOH 

 >    H2N<^  y—  />NH2.H2S04   > 


H2N<(  >NH2. 

Yield. — 75 — 80%  theoretical  (55 — 60  gms.).  Lustrous  plates;  M.P. 
128°  ;  B.P.  over  400°,  with  decomposition  ;  slightly  soluble  in  hot  water  ; 
soluble  in  alcohol  and  in  benzene.  Important  intermediate  for  dyestuffs. 
(Z.  a,  6,  67.) 

Pkeparatton  369. — o-Tolidine. 

CH3    CH3 

H2N<^   )NH,         C14H16N2.  212. 

The  process  is  exactly  the  same  as  for  benzidine  except  that  100  gms. 
of  distilled  nitrotoluene  (containing  no  more  than  4%  j9-nitrotoluene)  are 
used. 

CH3  CH3  CH3  CH3 

/      N  NH — NH  /      \    ->  Nh/  NnH.. 

Yield.— 65%0  theoretical  (48  gms.).  Plates;  M.P.  128°;  slightly 
soluble  in  water  ;  soluble  in  alcohol  and  in  benzene  ;  salts  about  5  times 
more  soluble  than  those  of  benzidine  ;  intermediate  for  dyestuffs.  (B.,  17, 
467  ;  20,  2017.) 

Reaction  CLXXI.  Action  of  Alkali  Sulphides  and  Hydrosulphides  on 
Nitro  Compounds. 

R.N02  ->  R.NH2. 

The  hydrogen  is  generated  in  the  solution  of  alkali  sulphide. 

Na2S  +  3H20  ->  Na2S03  +  3H2. 
Excess  of  NagS  is  used,  which  dissolves  the  sulphur  always  formed  in 


358  SYSTEMATIC  ORGANIC  CHEMISTRY 


the  reaction,  due  to  oxidation.  The  reaction  is  specially  useful  in  cases  of 
nitro  compounds  containing  more  than  one  nitro  group,  and  conditions 
can  be  chosen  such  that  only  one  nitro  group  is  reduced,  e.g., 

acid  ™, 

<        >N02  +  12H   >     /  )>NH2. 

\  '  solution    ^  ' 

Na2S  ™. 

The  reaction  is  really  an  extension  of  that  on  alkaline  reduction,  since 
the  solution  of  sodium  sulphide  in  water  is  alkaline.  The  complete 
equations  are  : 

R.N02  +  Na2S  +  H20        R.NH2  +  Na2S03. 
4R.N02  +  6NaSH  +  H20  ->  4R.NH2  +  3Na2S203. 

Preparation  370. — m-Nitraniline. 

 N02 

NH2/      V      C6H602N2.  138. 

This  experiment  should  be  performed  in  a  fume  cupboard. 

100  gms.  m-dinitrobenzene  are  placed  in  a  beaker  with  500  c.cs.  water 
and  heated  to  85°.  The  stirring  should  be  very  brisk.  245  gms.  sodium 
sulphide  (Na2S.9H20)  dissolved  in  200  c.cs.  water  is  then  allowed  to  drop 
in  from  a  funnel  during  10  minutes.  The  dinitrobenzene  is  reduced  to 
m-nitraniline.  The  end  of  the  reaction  may  be  recognised  by  "  spotting  " 
the  solution  on  filter  paper,  and  touching  with  iron  or  copper  sulphate 
solution.  When  the  black  stain  remains  for  20  seconds,  the  reduction  is 
finished  and  the  mixture  is  cooled  down  to  20°  by  adding  ice.  After 
standing  for  several  hours  the  m-nitraniline  is  filtered  off,  and  may  be 
recrystallised  from  boiling  water. 

_N02.  N02 
NO  /  \    ->    NH /_J> 

Yield.— 70%  theoretical  (58  gms.).    M.P.  112-4°  ;  B.P.  285°  ;  inter- 
mediate for  azo  dyestuffs.    (C.  Z.,  37,  299.) 
Preparation  371. — Picramic  Acid. 

NH2 

OH<^      ^N02.       C6H505N3.  199. 

not- 

10  gms.  picric  acid  and  10  gms.  caustic  soda,  35%,  are  dissolved  in 
600  c.cs.  water  in  a  large  flask  and  heated  up  to  55°  with  vigorous 
stirring,  when  a  solution  of  40  gms.  crystalline  sodium  sulphide  (Na2S.9H20) 
in  100  c.cs.  water  is  gradually  added. 

127-5  gms.  of  powdered  picric  acid  are  then  added  by  degrees,  concur- 


THE  LINKING  OF  HYDROGEN  TO  NITROGEN  359 


rently  with  220  gms.  sodium  sulphide  in  400  c.cs.  of  water.  The  addition 
of  the  picric  acid  should  end  at  the  same  time  as  the  sulphide  solu- 
tion. The  temperature  should  not  rise  above  65°,  ice  being  added,  if 
necessary.  Stirring  is  continued  for  about  10  minutes  after  all  has  been 
added,  and  then  400  gms.  ice  are  quickly  added.  The  sodium  salt  of 
picramic  acid  is  immediately  precipitated.  After  standing  for  10  hours 
it  is  filtered  of!  and  washed  with  brine. 

The  free  acid  is  obtained  by  stirring  up  the  sodium  salt  with  500  c.cs. 
water,  heating  to  80°,  and  acidifying  with  dilute  sulphuric  acid  until  just 
acid  to  Congo  Red. 

Yield. — Almost  theoretical  (8-5  gms.).  Red  needles,  soluble  in  water  ; 
M.P.  168°— 169°.    (See  also  A.,  88,  281  ;  96,  83.) 

Reaction  CLXXII.   Action  of  Reducing  Agents  on  Azo  Compounds. — 

H2 

X— N  :    N — Y  ->  X.NH2  +  H2N.Y. 

This  reaction  is  useful  for  determining  the  composition  and  constitution 
of  azo  dyes.  The  reducing  agents  employed  are  usually  metal  and  acid, 
zinc-dust  and  water  or  ammonia,  stannous  chloride,  or  sodium  hydro- 
sulphite  in  alkaline  solution.  The  reaction  is  carried  out  with  or  without 
heat,  until  the  suspended  or  dissolved  colour  gives  place  to  a  colourless 
product. 

Preparation  372. — a-Amino-/?-Naphthol. 


NH2 


iOH. 


C10H9ON.  159. 


50  gms.  Orange  II.  (see  Preparation  385)  are  dissolved  in  500  c.cs. 
boiling  water,  and  to  this  is  added  65  gms.  tin  dissolved  in  375  c.cs.  cone, 
hydrochloric  acid.  When  decolorisation  is  complete  the  solution  is 
filtered  quickly  and  on  cooling  the  hydrochloride  of  amino-naphthol 
separates  out  as  colourless  crystals. 

Oil  OH  _ 

/       \_N  =  N<"  ^>S03H    J*    <(      )>NH2  +  H2N<^  ^>S03H. 

/  \  /  \ 
\  /  \  / 

Fine  needles,  slightly  soluble  in  dilute  hydrochloric  acid  and  in  alcohol. 
(B.,  25,  980.) 
Preparation  373. — Amino  Salicylic  Acid. 

OH 


COOH^       y       C7H703N.  153. 
NH2 

A  mixture  of  50  gms.  of  aniline  hydrochloride,  60  gms.  of  cone,  hydro- 
chloric acid,  and  300  gms.  of  ice  is  diazotised  by  adding  a  solution  of 


360  SYSTEMATIC  ORGANIC  CHEMISTRY 


29  gms.  of  sodium  nitrite  in  100  c.cs.  of  water  to  the  mixture.  After 
15  minutes  the  diazonium  salt  is  run  into  a  solution  of  53-3  gms.  of  salicylic 
acid  in  220  gms.  of  crystallised  sodium  carbonate  and  a  litre  of  water. 
The  sodium  salt  separates,  is  filtered  and  washed  with  a  little  water. 
The  azo-compound  is  next  boiled  with  about  a  litre  of  water,  sodium 
hydroxide  solution  added  until  alkaline  and  dry  sodium  hyposulphite 
(about  135  gms.)  added  until  the  reduction  is  complete.  After  the  aniline 
is  removed  by  steam  distillation,  acid  is  added,  and  the  free  amino- 
salicylic acid  separates. 


)NH2    ->    (        >NNC1    ->    (        >N  =  N<  >OH 


COOH 

,  -f  H2N^  ^>OH 
COOH 

Decomposes  at  280°.    (B.,  32,  81.) 

Reaction  CLXXIII.   Action  of  Reducing  Agents  on  Nitroso  Compounds. 

E.NO  ->  E.NH2. 

The  reduction  is  usually  carried  out  in  acid  solution,  or  with  bisulphite. 
For  example,  see  Preparation  392. 

Reaction  CLXXIV.  Reduction  of  Oximes  to  Amines  with  Metallic 
Sodium  or  Sodium  Amalgam. 

\  4H  v 

:  NOH   >    ^>CH.NH2  +  H20. 

The  reaction  serves  for  the  production  of  amines  from  aldehydes  or 
ketones  through  the  oximes  of  these  bodies. 

Reduction  with  metallic  sodium  is  usually  carried  out  in  absolute 
alcoholic  or  moist  ethereal  solution.  Methyl,  ethyl  or  amyl  alcohol  may 
be  used,  but  for  various  reasons  absolute  ethyl  alcohol  is  the  most 
frequently  employed,  the  reaction  being  conducted  at  or  near  the  boiling 
point  of  the  alcohol.  When  ordinary  alcohol  (about  90%)  is  used,  the 
sodium  spurts  about  on  the  surface  of  the  liquid,  and  most  of  the  hydrogen 
escapes  as  gas.  With  the  absolute  alcohol,  the  sodium — with  the  excep- 
tion of  the  first  portions  added — melts  to  a  ball  which  remains  largely, 
and  at  times  completely,  immersed  in  the  liquid,  and  hence  the  hydrogen 
generated  is  more  liable  to  react.  In  some  cases  the  sodium  alcoholate 
formed  also  acts  as  a  reducing  agent,  and  is  thereby  converted  into  the 
sodium  salt  of  the  corresponding  acid. 

When  the  reduction  is  carried  out  with  sodium  amalgam  the  oxime 
is  dissolved  in  aqueous  alcohol,  and  acetic  acid  and  amalgam  added  at 
intervals  so  that  the  solution  is  slightly  acid  throughout  the  reduction. 

Preparation  37 4. — a-Phenylethylamine. 

C6H5CH(NH2)CH3.       C8HnN.  121. 

50  gms.  acetophenone  oxime  dissolved  in  100  c.cs.  absolute  ethyl 
alcohol  are  placed  in  a  litre  round-bottomed  flask  having  a  long  neck. 


THE  LINKING  OF  HYDROGEN  TO  NITROGEN  361 


The  flask  is  fitted  with,  a  cork  carrying  an  addition  tube  (p.  46),  and  the 
sloping  limb  of  the  latter  is  attached  to  a  reflux  water  condenser,  while 
the  vertical  limb  is  closed  with  a  cork.  A  bottle  containing  benzene  and 
pieces  of  bright  sodium  (about  50  gms.)  of  such  a  size  that  they  slip 
easily  down  the  addition  tube,  is  prepared.  The  flask  is  heated  on  a 
water  bath  until  the  alcohol  boils.  Pieces  of  sodium  (one  at  a  time)  are 
introduced  through  the  vertical  limb  of  the  addition  tube,  a  piece  of 
drawn-out  glass  rod  being  used  to  remove  the  sodium  from  the  bottle, 
and  the  benzene  adhering  need  not  be  removed  with  filter  paper.  The 
first  pieces  of  sodium  cause  vigorous  reaction,  but  the  reaction  soon 
becomes  moderate.  The  alcohol  is  kept  actively  boiling  all  the  time. 
When  the  reaction  becomes  sluggish  a  further  100  c.cs.  absolute  alcohol 
are  added,  and  addition  of  sodium  to  the  boiling  solution  is  continued, 
as  before.  Altogether  about  500  c.cs.  absolute  alcohol  and  40  gms. 
sodium  are  required.  The  addition  of  sodium  is  continued  until  a  test, 
carried  out  in  the  following  way,  shows  that  reduction  is  complete  : — 

A  sample  (about  2  c.cs.)  is  withdrawn,  diluted  with  an  equal  volume 
of  water,  and  about  2  c.cs.  cone,  hydrochloric  acid  added.  The  mixture 
is  boiled  for  a  minute,  and  a  portion  added  to  hot  Fehling's  solution 
(see  p.  496).  If  no  reduction  of  the  Fehling's  solution  takes  place  the 
reduction  of  the  oxime  is  complete. 

When  reduction  is  complete  the  flask  is  cooled  in  ice  water,  while  the 
contents  are  neutralised  by  the  gradual  addition  of  cone,  hydrochloric 
acid — through  a  tube  leading  underneath  the  surface  so  as  to  avoid  loss 
of  fumes.  The  sodium  chloride,  which  is  precipitated,  is  filtered  off  and 
washed  with  about  50  c.cs.  of  15%  hydrochloric  acid,  the  washings 
being  added  to  the  filtrate,  which  is  then  placed  in  a  porcelain  basin  and 
evaporated  nearly  to  dryness.  The  residue,  when  cold,  is  agitated 
for  some  time  with  an  excess  of  cone,  caustic  soda  solution  ;  phenyl- 
ethylamine  separates  on  the  surface,  and  the  lower  layer  contains 
solid  sodium  chloride.  The  liquors  are  decanted  from  the  solid  sodium 
chloride  into  a  separating  funnel ;  the  sodium  chloride  is  agitated  with  a 
little  ether,  which  is  also  decanted  into  the  funnel.  The  upper  layer  of 
ether  and  phenylethylamine  is  separated,  and  the  aqueous  layer  extracted 
a  second  time  with  ether.  The  ethereal  extracts  are  mixed  and  dried 
over  anhydrous  sodium  sulphate.  After  standing  overnight  the  sodium 
sulphate  is  filtered  off,  and  the  phenylethylamine  recovered  in  one  of  the 
following  ways  : — 

1.  By  distillation.  The  ether  is  first  removed,  and  the  phenylethyl- 
amine (B.P.  186°)  comes  over  at  180°— 190°.  Owing  to  the  fact  that 
phenylethylamine  is  volatile  to  a  considerable  extent  in  ether  vapour, 
this  separation  is  not  so  efficient  as  might  be  expected. 

Yield.— 80%  theoretical. 

2.  A  current  of  dry  carbon  dioxide  is  passed  into  the  cold,  dry  ethereal 
solution,  which  after  some  time  goes  almost  solid,  owing  to  the  precipita- 
tion of  the  carbamate  of  the  amine.  The  precipitate  is  filtered  off,  well 
pressed  down  on  the  funnel,  and  washed  with  a  little  pure  dry  ether. 
Carbon  dioxide  is  again  passed  into  the  filtrate  and  any  carbamate  formed, 


362  SYSTEMATIC  OKGANIC  CHEMISTEY 


filtered  off,  and  so  on,  until  the  final  nitrate  yields  no  precipitate  on  pro- 
longed passing  of  carbon  dioxide.  The  total  yield  of  carbamate  is  pressed 
out  on  a  porous  plate  to  dry.  If  it  is  desired  to  keep  for  some  time  it 
should  be  preserved  in  a  stoppered  bottle. 

C6H5C(NOH).CH3  ->  C6H5.CH(NH2).CH3. 
2C6H5CH(NH2)CH3  +  C02  ->  C6H5CH(CH3)NHCOONH3CH(CH3).C6H5. 

Yield  of  Carbamate. — 95%  theoretical  (calculated  on  oxime). 

Since  the  carbamate  is  very  soluble  in  alcohol,  pure  ether  should  be 
used  for  the  extraction  when  the  base  is  recovered  as  carbamate.  The 
carbamate  may  be  used  directly  for  the  resolution  of  the  base  (see  p.  401). 

a-Phenylethylamine. — B.P.  186°  ;  easily  soluble  in  organic  solvents ; 
moderately  soluble  in  water  ;  strong  base  ;  absorbs  carbon  dioxide  when 
exposed  to  air. 

a-Phenylethylamine  Carbamate. — M.P.  101° — 102°  ;  easily  soluble  in 
water  or  in  alcohol ;  on  heating,  dissociates  into  amine  and  carbon 
dioxide.    (J.  C.  S.,  83,  1147.) 


CHAPTER  XXIV 


hydrogen  to  nitrogen 

Hydroxylamines  and  Hydrazines. 

Reaction  CLXXV. — Action  of  Metallic  Zinc  on  Nitro  Compounds  in 
Neutral  Solution. 

E.N02  +  4H  ->  E.NHOH 

e.g.,  nitrobenzene  gives  phenylhydroxylamine.  Although  the  reaction 
may  be  carried  out  by  generating  the  hydrogen  by  the  interaction  of 
zinc  and  water,  better  yields  are  obtained  by  adding  a  neutral  salt,  such 
as  ammonium  chloride. 

In  order  to  prevent  the  reduction  going  too  far,  it  is  necessary  to  keep 
down  the  temperature. 

Preparation  375. — Phenylhydroxylamine  ( (Hydroxy-amino)-benzene). 

C6H5NHOH.       C6H7ON.  109. 

12  gms.  of  nitrobenzene  are  mixed  in  a  beaker  with  250  c.cs.  of  water 
containing  6  gms.  of  ammonium  chloride  and  well  stirred,  the  temperature 
being  kept  below  15°.  18  gms.  of  good  zinc-dust  are  added  in  four  equal 
parts  after  intervals  of  J  hour.  When  the  smell  of  nitrobenzene  has 
disappeared  the  stirring  is  stopped.  The  mixture  is  filtered  at  the  pump, 
the  filtrate  being  put  on  one  side,  and  the  precipitate  washed,  by  adding 
200  c.cs.  of  water  at  45°  while  the  pump  is  not  working,  and  then  the 
water  gradually  sucked  through  by  means  of  the  pump.  The  filtrate 
and  the  washings  are  separately  saturated  with  sodium  chloride,  and 
cooled  to  0°.  After  a  short  time  the  phenylhydroxylamine  separates 
out ;  it  is  filtered  and  dried  without  washing. 

/      \N02    ->    /  ^NH.OH. 

Yield. — Almost  theoretical  (10  gms.).  Colourless  crystals  ;  M.P.  81°  C. 
(D.R.P.,  89978.) 

Reaction  CLXXVI.  Action  of  Reducing  Agents  on  Diazonium  Compounds. 

EN  =  NCI  +  4H  ->  R.NH.NH2. 

The  reaction  is  somewhat  similar  to  that  of  reducing  agents  on  azo- 
compounds.  The  hydrazines  are  universally  obtained  by  this  reaction, 
the  same  reducing  agents  being  used  as  in  the  case  of  azo-compounds. 

Preparation  376 . — £>-Nitrophenylhydrazine. 

N02<^      ^>NH.NH2.       C6H702N3.  153. 

10  gms.  of  j9-nitraniline  are  diazotised  (see  p.  367).    The  filtered  diazo- 

363 


364 


SYSTEMATIC  ORGANIC  CHEMISTRY 


solution  is  slowly  added,  with  stirring,  to  40  cues,  of  a  cold  saturated 
solution  of  ammonium  sulphite  (see  p.  508)  containing  8  c.cs.  of  cone, 
ammonia  solution.  Ammonium  nitrophenylhydrazine  disulphonate  soon 
separates,  and  after  standing  for  about  an  hour  in  a  freezing  mixture, 
is  filtered,  and  the  precipitate  heated  on  the  water  bath  with  20  c.cs. 
cone,  hydrochloric  acid  for  a  few  minutes  at  70° — 80°.  The  solution 
thus  obtained  is  cooled  in  ice,  and  the  precipitate  which  separates  is 
dissolved  in  a  small  quantity  of  water.  To  this  solution  a  cold  concen- 
trated solution  of  sodium  acetate  is  added ;  the  nitrophenylhydrazine 
separates  and  is  recrystallised  from  alcohol. 

N02<^       \NH2    ->    N02<^      \n2C1    ->    N02<^  ^>NH.NH2. 

Yield. — 15 — 20%  theoretical  (2  gms.).  Orange  red  needles;  M.P. 
157°,  with  decomposition ;  soluble  in  alcohol  and  in  ligroin.  (J.  C.  S., 
121,  719.) 

Peepaeation  37 7 . — Phenylhydrazine. 

C6H5NH.NH2.       C6HSN2.  108. 

Method  I. — 10  gms.  freshly  distilled  aniline  are  added  to  a  solution  of 
30  gms.  cone,  hydrochloric  acid  in  75  c.cs.  water  and  diazotised  with 
8  gms.  sodium  nitrite  in  30  c.cs.  water,  the  temperature  being  kept  about 
0°.  30  gms.  common  salt  are  added  with  shaking,  and  the  solution  cooled 
in  a  freezing  mixture.  60  gms.  stannous  chloride  in  25  gms.  cone, 
hydrochloric  acid  are  then  added,  and  after  standing  for  some  hoursL  the 
hydrochloride  of  phenylhydrazine  separates,  is  filtered  off  and  washed 
with  a  little  saturated  salt  solution.  It  is  transferred  to  a  flask  and 
treated  with  excess  of  caustic  soda  solution,  when  the  free  base  is 
extracted  with  ether.  The  ethereal  solution  is  dried  with  caustic  potash, 
and  the  ether  removed  by  evaporation.  The  phenylhydrazine  may  be 
purified,  if  desired,  by  freezing  or  by  distilling  in  vacuo. 

.  H2 

C6H5NH2  ->  C6H5N2C1  >  C6H5NH.NH2.HC1. 

Yield. — 90%  theoretical  (10  gms.). 

Method  II. — 10  gms.  aniline  are  dissolved  in  acid  and  water  and 
diazotised  as  before.  The  diazo  solution  is  poured  into  a  saturated 
solution  of  sodium  sulphite  containing  34  gms.  Na2S03.  The  liquid  is 
now  heated  with  zinc  dust  and  a  little  acetic  acid  till  it  becomes  colourless, 
when  it  is  filtered  hot.  Sodium  phenylhydrazine  sulphonate  passes  into 
the  filtrate,  and  is  immediately  mixed  with  one-third  of  its  volume  of 
fuming  hydrochloric  acid  (caution !)  which  converts  it  into  phenyl- 
hydrazine  hydrochloride,  which  is  thrown  out  of  solution,  filtered,  and 
well  pressed.    The  free  base  is  liberated  as  before. 

Yield. — 75%  theoretical  (8  gms.).  Colourless  crystals  ;  M.P.  23°  ; 
B.P.763  243-5°  (decomposition);  B.P.12  120°;  soluble  in  alcohol,  ether, 
benzene.    (B.3  16,  2976  ;  26,  19  ;  31,  346.) 


CHAPTER  XXV 


the  linking  of  nitrogen  to  nitrogen 

Diazonium  Compounds. 

Reaction  CLXXVIX. — Action  of  Nitrous  Acid  on  Primary  Aromatic 
Amines. 

Diazonium  compounds  are  formed  in  this  way. 
C6H5NH2  +  HN02  +  HC1 


C6H5NH2  +  NaN02  +  2HC1 


Diazonium  compounds  are  usually  prepared  in  mineral  acid  solution, 
and  the  nitrous  acid  generated  from  sodium  nitrite.  Sufficient  acid  must  be 
used  to  generate  nitrous  acid  and  to  form  the  salt  of  the  base,  and  still 
leave  the  solution  acid.  In  practice  2| — 2J  mols.  of  hydrochloric  acid  are 
generally  employed.  In  most  cases  it  is  essential  that  the  reaction  should 
be  carried  put  at  about  0°,  as  many  diazo  solutions  decompose  above  this 
temperature.  The  reaction  goes  very  readily  in  some  cases  ;  but  in  others, 
and  especially  where  an  acid  group  is  present,  e.g.,  naphthylamine  sul- 
phonic  acids,  the  reaction  is  only  carried  out  with  difficulty.  It  is 
possible  to  diazotise  a  solid,  but  the  reaction  is  very  slow,  and  if  the  solid 
is  dissolved  and  reprecipitated  in  a  fine  state  of  division  the  action  goes 
much  quicker. 

In  the  case  of  acidic  substances,  the  compound  is  dissolved  in  sodium 
carbonate  or  caustic  soda  solution,  and  reprecipitated  with  the  requisite 
amount  of  acid  and  then  diazo tised. 

Compounds  such  as  [1.2.4]  amido-hydroxy-sulphonic  acid  of  naphthalene 
and  its  isomers  cannot  be  diazotised  in  mineral  acid,  as  quinone  com- 
pounds are  formed,  due  to  oxidation.  They  are  diazotised  in  neutral 
solution  in  presence  of  copper  or  zinc  salts,  or  in  weak  acid  solution, 
such  as  acetic  acid.    (D.R.P.,  171024.) 

Diazotisation.— In  the  ordinary  process  of  diazotisation  the  base  is 
dissolved  in  the  requisite  quantity  of  acid,  with  heating  if  necessary, 
and  excess  of  ice  is  added  to  bring  the  temperature  down  to  0°— 5°. 
Sodium  nitrite  in  the  form  of  a  10%  solution  is  then  run  in  until  the  end 
point  is  reached. 

The  End  Point. — The  reaction  is  complete  when  on  stirring  after  each 
addition,  and  testing  with  starch  iodide  or  starch  iodide  paper,  a  distinct 

365 


->  C6H5NC1  +  2H20. 

ill 

N 

C6H5NC1  +  NaCl  +  2ELO. 

I 


366  SYSTEMATIC  OEGANIC  CHEMISTRY 


blue  colour  is  obtained  at  once.  A  drop  of  the  solution  is  removed  on  a 
glass  rod  at  intervals  and  placed  on  the  starch  iodide  paper,  or  on  a  piece 
of  dry  filter  paper  near  a  drop  of  starch-iodide  solution  (see  p.  501) .  When- 
ever the  blue  colour  is  obtained,  and  this  colour  persists  when  another  test 
is  made  after  3  minutes,  the  reaction  is  complete.  A  blue  colour  developed 
on  the  starch  paper  after  a  time  is  discarded.  The  nitrite  should  be 
added  at  such  a  rate  that  no  free  nitrous  acid  is  evolved.  It  is  essential 
that  the  starch  iodide  solution  or  paper  should  be  tested  previously  by 
a  very  dilute  acidified  solution  of  sodium  nitrite  before  any  test  is  made. 

It  is  not  usually  necessary  to  isolate  the  diazo  salt  from  solution, 
although  in  some  cases  this  separates  out  as  the  reaction  proceeds.  If 
sufficient  acid  is  not  present,  an  amido  azo  compound  may  be  precipitated, 
due  to  the  "  coupling  "  (see  p.  275)  of  the  diazonium  compound  with  the 
excess  of  base.  In  fact,  this  is  one  method  of  forming  amido  azo  com- 
pounds— by  diazo tising  in  presence  of  about  half  the  quantity  of  acid 
necessary  for  the  complete  diazotisation. 

Some  diazonium  compounds  are  quite  stable,  e.g.,  o-anisidine,  while 
2>-nitraniline  is  stable  up  to  30°. 

Stable  Diazonium  Compounds. — Many  methods  have  been  devised  for 
preparing  stable  diazonium  compounds  for  use  in  the  dyeing  industry. 
For  example,  diazotised  j?-nitraniline,  when  treated  with  alkali,  forms 

a  compound,  N02<^      ^)>N  —  NONa,  which  is  perfectly  stable,  and  can 

be  converted  back  to  the  diazonium  compound  with  hydrochloric  acid. 

When  the  diazonium  compound  is  treated  with  /? -naphthalene  sulphonic 
acid  (Na  salt)  a  stable  diazonium  compound  is  produced  (Thann  and 
Becker). 


R — N  CI  +  Na  SO 


Preparation  378. — Diazonium  Compounds  (in  Solution). 

1.  Aniline. 

C6H5NNC1. 

9-3  gms.  aniline  are  run  into  100  gms.  of  water  and  45  gms.  cone,  hydro- 
chloric acid.  100  gms.  ice  are  added,  and  the  whole  is  stirred  till  tempera- 
ture reaches  0°.  7  gms.  sodium  nitrite  (as  a  10%  solution)  are  then  gradu- 
ally added,  preferably  by  a  tube  leading  under  the  surface  of  the  solution. 
The  temperature  should  not  rise  above  7° — 8°.  Slow  stirring  is  continued 
all  the  time,  except  when  tests  are  being  made.  When  a  distinct  blue 
colour  is  obtained  on  starch  iodide  paper  at  once,  which  persists  after 
another  test  in  3  minutes,  the  diazotisation  is  complete. 

2.  Benzidine  and  Tolidine. 

C1N2C6H4— C6H4N2C1. 

The  process  is  similar  to  above,  184  gms.  benzidine  o^l-2  gms.  tolidine 
being  dissolved  by  heating  in  300  gms.  water  and  90  gms.  cone,  hydro- 


THE  LINKING  OF  NITROGEN  TO  NITROGEN  367 

chloric  acid.  After  cooling  to  0°,  the  diazotisation  is  carried  out  as  before. 
In  these  cases  tetrazonium  compounds  are  formed. 

3.  p-Nitraniline. 

N02C6H4N2C1. 

(a)  13-8  gms.  j9-nitraniline  are  powdered  and  added  to  a  mixture  of 
150  gms.  water,  45  gms.  cone,  hydrochloric  acid,  and  150  gms.  ice,  and 
stirred  for  15  minutes,  the  temperature  being  under  5°.  7  gms.  sodium 
nitrite  (10%  solution)  is  introduced  quickly,  the  usual  test  with  starch- 
iodide  being  applied  after  all  of  the  nitrite  solution  has  been  added. 

(6)  13-8  gms.  jo-nitraniline  are  added  to  70  gms.  water  and  45  gms.  cone, 
hydrochloric  acid,  and  heated  to  dissolve.  The  solution  is  then  cooled 
and  diazotised,  as  before. 

4.  H  Acid. 


OH  NNC1 


34-1  gms.  H  acid  are  introduced  into  400  gms.  water  and  6  gms.  sodium 
carbonate  at  a  temperature  of  40° — 50°.  The  solution  should  be  alkaline. 
This  is  run  into  a  mixture  of  55  gms.  hydrochloric  acid  and  500  gms. 
water.  7  gms.  sodium  nitrite  (10%  solution)  are  then  added — as  before — 
slowly  towards  the  end. 

5.  Dinitroanihne. 

NO,/"  ^N2C1. 
N02 

Sodium  nitrite  (1^  mols.)  is  dissolved  in  cone,  sulphuric  acid  by  heating 
to  about  50°.  It  is  then  cooled  to  20°,  and  finely  powdered  dinitroanihne 
(1  mol. )  is  gradually  added.  When  all  has  been  added,  stirring  is  continued 
for  2  hours  at  20° — 30°.  The  solution  is  then  poured  on  to  ice  and 
filtered.    The  diazonium  compound  is  thus  isolated  as  a  paste. 

Preparation  379. — Diazoaminobenzene. 

C6H5N  =  N.NH.C6H5.       C12.HnN3.  197. 

6  gms.  of  sulphuric  acid  and  600  c.cs.  of  water  are  placed  in  a  litre  beaker, 
and  20  gms.  of  aniline  added.  The  solution  is  warmed  to  30°,  and  a 
solution  of  7-5  gms.  of  sodium  nitrite  dissolved  in  a  little  water  added  with 
constant  stirring.  The  solution  is  maintained  at  30°  for  15  minutes, 
after  which  it  is  left  to  stand  for  30  minutes  at  laboratory  temperature. 
The  diazoamino  benzene  is  then  filtered  off,  washed  with  water,  and  dried 
on  a  porous  plate.  It  may  be  recrystallised  from  warm  petroleum,  but 
the  solution  should  not  be  boiled  for  any  length  of  time  as  the  compound 
is  thereby  decomposed. 

C6H6N  :  N.H$04  +  NH2.C6H5  ->  C6H5N  :  N.NHC6H5  +  H2S04. 

7^.-80%  theoretical  (17  gms.).  Golden-yellow  plates  ;  M.P.  28°  ; 
explodes  when  heated  slightly  above  its  M.P. 


368  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  380. — Diazobenzene  Sulphate  (Benzene  Diazonium  Sul- 
phate). 

C6H5.N(:  N).S04H.       C6H604N2S.  202. 

15  gms.  (1  mol.)  of  aniline  and  140  gms.  of  absolute  alcohol  are  mixed, 
and  30  gms.  (2  mols.)  of  cone,  sulphuric  acid  run  in,  slowly  and  with 
constant  shaking.  The  precipitate  of  aniline  sulphate,  which  first 
appears,  redissolves.  The  mixture  is  kept  at  30° — 35°  (thermometer 
in  liquid),  out  of  direct  sunlight,  while  20  gms.  (1  mol.)  of  amyl  nitrite 
are  dropped  in  from  a  tap-funnel.  The  whole  is  then  left  in  ice  water 
for  \  hour,  and  the  crystals  which  have  separated  filtered  off  at  the  pump 
and  washed  with  a  little  alcohol.  As  diazobenzene  sulphate  is  explosive 
the  precipitate  must  be  kept  moist.  In  that  state  it  can  be  used  for  the 
various  reactions  described  below.* 

(C6H5NH2)2H2S04  +  2C5HuONO  +  H2S04  = 
2C6H5N(  i  N)S04H  +  2C5HnOH  +  2H20. 

Colourless  needles  ;  soluble  in  water  and  methyl  alcohol ;  slightly 
soluble  in  ethyl  alcohol ;  on  heating  decomposes  explosively  at  about  100°. 
(A,  137,  47  ;  B.,  28,  2049.) 

Preparation  381. — Diazobenzene  Nitrate  (Benzene  Diazonium  Nitrate). 

C6H5.N(;N).N03.       C6H503N3.  167. 

Owing  to  the  highly  explosive  nature  of  the  diazobenzene  nitrate,  its 
preparation  should  never  be  undertaken  except  the  compound  is  wanted 
for  research  or  some  special  purpose.  20  gms.  of  aniline  are  placed 
in  a  beaker,  well  cooled,  and  "boiled-out"  nitric  acid,  previously 
diluted  with  half  its  volume  of  water  carefully  added,  till  the  mixture 
sets  to  a  thick  crystalline  paste — aniline  nitrate.  The  crystalline  mass  is 
filtered  off  at  the  pump,  and  washed  with  a  little  cold  water.  5  gms.  of 
the  moist  salt  are  finely  powdered  and  placed  in  a  small  flask  with  enough 
water  just  to  cover  the  substance.  The  flask  is  now  well  cooled  in  ice- 
water,  and  nitrous  fumes  (for  preparation,  see  p.  509)  are  led  in  with 
frequent  agitation  until  all  the  aniline  nitrate  has  disappeared.  At  no 
time  must  the  temperature  of  the  flask  rise  above  10°.  Should  there  not 
be  sufficient  water  to  keep  all  the  diazobenzene  nitrate  formed  in  solution, 
its  crystalline  form  will  easily  enable  it  to  be  distinguished  from  the 
aniline  salt.  When  the  reaction  is  finished  the  contents  of  the  flask  are 
poured  into  3  times  their  volume  of  absolute  alcohol,  and  ether  is  added 
to  this  mixture  as  long  as  crystals  separate.  If  too  much  water  has  been 
added  to  the  aniline  nitrate  from  the  beginning,  a  thick  aqueous  solution 
of  diazobenzene  nitrate  separates  out  in  place  of  the  crystals.  If  this 
occurs,  the  ether-alcohol  is  decanted  off,  and  the  residue  redissolved  in 
absolute  alcohol,  and  reprecipitated  with  ether.  On  no  account  must 
large  quantities  of  the  preparation  be  allowed  to  dry.    If  it  has  to  be 

*  Any  of  the  diazo -compound  which  remains  over  should  hd  dissolved  inl 
wuter  and  poured  away. 


THE  LINKING  OF  NITROGEN  TO  NITROGEN  369 


preserved  it  must  be  kept  moist,  or,  better,  in  aqueous  solution.  The 
usual  diazo  reactions  can  be  carried  out  with  the  latter. 

C6H5.NH2  +  HN03  =  C6H5NH3.N03. 
2C6H5.NH3.N03  +  NO  +  N02  =  2C6H5.N(  \  N).N03  +  3H20. 

Colourless  needles  ;  extremely  explosive  in  the  dry  state  ;  very  soluble 
in  water  ;  insoluble  in  ether  ;  on  heating  decomposes  explosively.  (A., 
137,  41.) 

Reactions  of  Diazonium  Compounds. 

The  following  reactions  are  performed  in  test  tubes  with  about  1  gm. 
of  the  substance.    Most  of  these  reactions  are  also  given  on  the  large  scale. 

1.  The  substance  is  heated  with  a  few  cubic  c.cs.  of  ethyl  alcohol,  when 
vigorous  effervescence  takes  place,  and  the  liquid  turns  red.  On  adding 
water  an  oil  consisting  of  benzene  and  a  little  phenetole  separates  on  the 
surface. 

C6H5.N2.S04H  +  C2H5OH  =  C6H6  +  N2  +  CH3.CHO  +  H2S04. 
C6H5.N2.S04H  -f  C2H5OH  =  C6H5.O.C2H5  +  N2  +  H2S04. 

2.  A  solution  of  about  1  gm.  of- the  substance  in  a  little  water  is  cooled 
in  ice,  made  alkaline  with  caustic  soda,  and  treated  with  a  cold,  alkaline 
solution  of  stannous  hydrate,  made  by  dissolving  about  4  gms.  of  stannous 
chloride  in  twice  its  weight  of  water,  and  adding  40%  caustic  soda  solu- 
tion until  the  precipitate  redissolves.  Effervescence  occurs,  nitrogen  is 
liberated,  and  benzene  separates  on  the  surface  of  the  liquid. 

C6H5.N2.ONa  +  Sn(ONa)2  +  H20  =  C6H6  +  0  :  Sn(ONa)2  +  N2  +  NaOH. 

3.  An  aqueous  solution  of  the  substance  is  gently  warmed,  when  a 
vigorous  evolution  of  nitrogen  occurs,  and  a  dark-coloured  oil,  smelling 
strongly  of  phenol,  separates.  It  can  be  extracted  with  ether  and  tested 
for  phenol  (see  p.  347): 

If  a  solution  of  diazobenzene  nitrate  be  used,  the  liberated  nitric  acid 
acts  on  the  phenol  as  it  is  formed,  and  nitrophenol  is  produced. 

C6H5.N2.S04H  +  H20  =  C6H5OH  +  H2S04  +  N2. 
C6H5.N2.HN03  +  H20  =  C6H5OH  +  HN03  +  N„ 
C6H5OH  +  HN03  =  C6H4(OH)(N02)  +  H20. 

4.  An  aqueous  solution  of  the  substance  is  mixed  with  a  solution  of 
bromine  in  hydrobromic  acid  or  potassium  bromide,  when  a  reddish- 
brown  oil  separates.  This  solidifies  to  a  mass  of  leafy  crystals,  if  the 
aqueous  layer  be  poured  off  the  oil,  and  the  latter  washed  with  a  little 
ether.    The  crystals  are  diazobenzene  perbromide. 

C6H5.N2.S04H  +  KBr  +  Br2  =  C6H5NBr.NBr2  +  KHS04. 
C6H5.N2.S04H  +  HBr  +  Br2  =  C6H5.NBr.NBr2  +  H2S04. 

If  a  sufficient  quantity  of  the  crystals  has  been  prepared,  it  may  be 
divided  into  two  portions.  One  portion  is  covered  with  cone,  ammonia. 
A  violent  reaction  sets  in,  the  crystals  disappear,  and  a  dark  oil,  possessing 

S.O.C.  B  B 


370  SYSTEMATIC  ORGANIC  CHEMISTRY 


a  peculiar  narcotic  odour,  is  produced,  consisting  principally  of  diazo- 
benzene  imide. 

C6H5NBrNBr2  +  NH3  -  C6H5N3  +  3HBr. 

The  other  portion  of  the  perbromide  is  warmed  with  a  little  alcohol. 
Nitrogen  and  bromine  are  given  off,  and  bromobenzene  is  formed. 

C6H5.NBr.NBr2  =  C6H5Br  +  N2  +  Br2. 

5.  Potassium  iodide  solution  is  added  to  an  aqueous  solution  of  the 
diazonium  salt.  Nitrogen  is  evolved,  and  a  dark-coloured  oil,  iodobenzene, 
separates. 

C6H5.N2.S04H  +  KI  =  C6H5I  +  N2  +  KHS04. 
For  large  scale  reaction  see  Praparation  338. 

6.  The  solution  of  the  diazonium  salt  is  mixed  with  an  aniline  salt  and 
excess  of  sodium  acetate,  or  the  solution  is  shaken  up  with  a  few  drops 
of  aniline.  In  either  case  a  yellow  crystalline  precipitate  of  diazoamino- 
benzene  is  obtained. 

C6H5.N2.S04H  +  C6H5NH2.HCJ]  +  CH3€OONa  = 
C6H5N  :  N.NHC6H5  +  NaHS04  +  CH3COOH  +  HC1. 
C6H5.N2.S04H  +  C6H5NH2  =  C6H5N2.NHC6H5  +  H2S04. 

For* large  scale  reaction  see  p.  367. 

7.  A  solution  of  phenol  in  caustic  soda  is  added  drop  by  drop  to  an 
aqueous  solution  of  the  substance.    An  orange  crystalline  precipitate  of 

*  sodium  hydroxyazobenzene  is  formed.  If  /?-naphthol  be  used  in  place 
oT  phenol  a  scarleT^precipitate  of  sodium  hydroxy-^-naphthaleneazo- 
benzene  is  obtained  (Sudan  Dyes). 

C6H5.N2.S04H  +  C6H5(ONa)  =  C6H5N  :  NC6H4(ONa)  +  Na2S04  +  2H20. 
G6H5.N2S04H  +  C10H7(ONa)  =  C6H5N  :  NCloH6(ONa)  +  Na2S04  +  2H20. 

8.  An  acetic  acid  solution  of  dimethylaniline  is  added  to  a  solution 
of  the  substance.  A  magnificent  red  colour  is  produced  in  a  short  time 
through  the  formation  of  dimethylaminoazobenzene  sulphate. 

C6H5N2S04H  +  C6H5N(CH3)2.HOOC.CH3  = 
C6H5N  :  N.C6H4N(Ca3)2.H2S04  +  CH3COOH. 

A  sulphuric  acid  solution  of  m-phenylene  diamine  is  added  to  the  solution 
of  the  diazonium  salt.  The  orange  colour  is  due  to  diaminoazobenzene 
sulphate  (Chrysoidine). 

C6H5N2S04H  +  C6H4(NH2)2(H2S04)  = 
C6H5N  :  NC6H3(NH2)2(H2S04)  +  H2S04. 

For  large  scale  reaction  see  Preparation  384. 

9.  A  \  grn.  at  the  most  of  the  moist  diazobenzene  sulphate  is  allowed 
to  dry  spontaneously  on  filter  paper  in  some  safe  place,  and  when  dry 
exploded  by  kindling  the  paper. 


THE  LINKING  OF  NITROGEN  TO  NITROGEN  371 


Reaction  CLXXVIII.  Action  of  Alkaline  Reducing  Agents  on  Aromatic 
Nitro  Compounds. — Azoxy  and  azo  compounds  are  first  formed. 

2R.N02 


and 

The  final  reduction  product  is  a  hydrazo  compound.  In  order  to  isolate 
the  azoxy  and  azo  compounds,  the  requisite  quantity  of  reducing  agent  is 
employed.  For  example,  if  zinc  is  used,  then  three-fifths  and  four-fifths 
of  the  quantity  necessary  for  complete  reduction  will  give  the  azoxy 
and  azo  compounds  respectively,  the  conditions  being  the  same  (see 
Preparation  368). 


R.N — N.R  and  R — N  =  N.R 


0  0 

Azoxy 

R — N  =  N.R. 

Azo 


B  B  2 


CHAPTER  XXVI 


DYES 


1.  Azo  Dyes. 

These  dyestuffs  are  formed  by  coupling  diazonium  compounds  with 
phenols  or  aromatic  bases.  The  characteristic  group  is  — X  =  X — . 
and  the  general  formula  X— X  =  X—  Y.  Mono-azo  dyes  contain  one 
—  X  =  X—  group,  while  dis-azo  dyes  contain  two,  and  so  on.  For  the 
general  laws  of  coupling  see  Eeaction  CXXII.  Mono-azo  dyes  are  acid 
\  or  basic  in  reaction,  according  to  the  nature  of  the  auxochrome  present 
W».e  p.  275).  They  are  soluble  in  alkali  and  in  cone,  sulphuric  acid  if 
they  contain  a  phenol  or  a  sulphonic  group.  They  are  decomposed  by 
cone,  nitric  acid  and  halogens.  Reducing  agents  decompose  them,  with 
the  formation  of  amines,  a  reaction  which  serves  to  determine  their 
composition  and  constitution. 

X— X  =  X— Y  -h  4H  ->  X.XH2  +  XH2.Y. 

Preparation  382. — Methyl  Orange  (Helianthine). 

S03Xa/      \n  =  N<C      V(CH3)2-       C14H1403X3SXa.  J21. 


17-3  gms.  of  sulphanihc  acid  are  dissolved  in  150  c.cs.  water  containing 
6  gms.  sodium  carbonate  in  solution.  To  this  solution  are  added  7-2  gms. 
of  sodium  nitrite  in  10%  solution.  The  mixture  is  cooled  by  adding 
ice,  and  3-6  gms.  of  anhydrous  hydrochloric  acid  in  the  form  of  a  15% 
solution  (see  p.  509),.  slowly  added  with  stirring.  12-1  gms.  of  dimethvl- 
aniline  are  dissolved  in  an  equal  quantity  of  hydrochloric  acid  as  above, 
and  added  to  the  diazonium  compound.  Caustic  soda  solution  is  then 
added  till  the  solution  is  just  alkaline.  The  Methyl  Orange  separates  at 
once.  A  further  yield  may  be  obtained  by  adding  common  salt  until 
solution  is  saturated.  The  dyestuff  is  filtered  off,  and  is  recrystallised 
from  water. 


S.O3H/       ^>NH^->    S03H<^  \N2C1 


dimethyl  aniline 


S03H<^  \x  =  N<(  .^>N(CH3)2. 

Yield. — Almost  theoretical.    (B.,  10,  528.) 

The  yellow  crystals  are  the  sodium  salt,  and  when  acid  is  added  to  a 
solution  a  red  colour  is  obtained.  The  dyestuff  is,  therefore,  used  as  an 
indicator  in  acidimetry  and  alkalimetry. 

372^ 


DYES 


373 


If  anthranilic  acid  is  used  in  place  of  sulphanilic,  the  dyestuff  formed  is 
Methyl  Red.  (See  "  Organic  Syntheses,"  Vol.  II.  (1922),  J.  B.  Conant  and 
others.) 

_COOH 
<^  ^>N  =  _\n(CH3)2. 

Preparation  383.— Congo  Red. 

NH2  NH2 

\  /   \_/         I      I  I 


C8aH2606N6S2.  653. 


184  gms.  benzidine  are  dissolved  in  300  c.cs.  of  water  and  20  c.cs.  cone, 
hydrochloric  acid,  heat  being  applied,  if  necessary.  Ice  is  added  till  the 
temperature  is  below  5°  C.  30  c.cs.  cone,  hydrochloric  acid  are  then  added, 
and  about  144  gms.  sodium  nitrite  in  10%  solution  until  diazotisation  is 
complete  (see  p.  365).  150  gms.  sodium  naphthionate  are  dissolved  in  as 
little  water  as  possible.  The  diazo  solution  is  rim  into  the  sodium 
naphthionate,  with  stirring,  and  after  \  hour  a  solution  of  35  gms.  sodium 
carbonate  is  added  gradually,  so  that  during  further  stirring  the  solution 
is  always  alkaline.  The  contents  of  the  beaker  will  appear  brown  at  this 
stage.  The  whole  is  then  slowly  heated  up  to  about  80°  C.  and  common 
salt  added  to  saturate  the  solution.  After  cooling,  the  reddish-brown 
Congo  Red  is  filtered  off,  washed  with  saturated  common  salt  solution, 
and  dried.    Dyes  cotton,  direct  from  alkaline  bath,  red. 

In  order  to  obtain  a  good  yield  a  large  excess  of  sodium  naphthionate 
is  employed,  the  excess  being  recovered  as  the  free  acid  on  acidifying  the 
mother  liquor  after  filtering  off  the  dyestuff.    (B.,  19,  1719.) 

If  o-tolidine  is  used  in  place  of  benzidine,  the  dyestuff  formed  is  Benzo- 
purpurin  4=B.    (D.R.P.,  84893.) 

Preparation  384. — Chrysoidine  Y. 


\N  =  N<f      \nH2.HC1.  C12H13N4C1. 


248-5. 


9-3  gms.  aniline  are  mixed  with  100  c.cs.  water.  Ice  is  added  and 
30  c.cs.  (tone,  hydrochloric  acid.  The  solution  is  then  diazotised  by 
adding  gradually  about  7-2  gms.  sodium  nitrite  in  10%  solution  (see 
p.  365).    The  solution  should  be  kept  below  5°  C. 

11  gms.  m-phenylenediamine  are  dissolved  in  200  c.cs.  water,  and  made 
just  acid  with  hydrochloric  acid.  The  diazo  solution  is  then  poured  into 
the  diamine  solution,  and  the  whole  stirred  for  some  time,  until  coupling 
is  complete.    Test  (see  p.  490). 

The  solution  is  heated  to  about  60°  C,  and  common  salt  added  to 
saturate  the  solution.  After  standing  till  cold,  the  chrysoidine  separates 
out  as  reddish-brown  crystals,  which  are  filtered  off,  washed  with 
saturated  common  salt  solution,  and  dried. 


374  SYSTEMATIC  ORGANIC  CHEMISTRY 


Dyes  wool,  silk,  and  tannin-mordanted-cotton  orange. 

/      ^)NH2  ^    /      ^>N  =  NCI. 

NH9  ~  NH 

/       \N  =  NCI  +  /       \NH2  ->  /       ^>N  =  N— / 

(B.,  10,  388.) 

If  m-tolylenediamine  is  used  in  place  of  m-phenylenediamine,  the 
dyestuff  formed  is  Chrysoidine  R. 
Peeparation  385. — Orange  II. 


OH 

SOoH<^      \_N  =  N— / 


C16H1204N2S.  328. 


17-3  gms.  sulphanilic  acid  are  dissolved  in  water  and  a  little  caustic  soda. 
Ice  is  added  until  the  temperature  is  below  5°  C.  30  c.cs.  hydrochloric 
acid  are  then  added,  and  about  7-2  gms.  sodium  nitrite  in  10%  solution 
gradually  run  in  until  diazotisation  is  complete  (see  p.  365).  The  diazo 
compound  usually  separates  out  as  fine  needles,  but  these  are  not  isolated. 
144  gms.  /?-naphthol  are  dissolved  in  15  c.cs.  water,  to  which  4-5  gms. 
caustic  soda  have  been  added.  This  solution  is  made  up  to  about  180  c.cs. 
by  adding  water.  It  is  then  cooled,  if  necessary.  The  diazo  solution  is 
carefully  added,  with  stirring,  until  coupling  is  complete  (see  p.  490). 
The  mass  should  now  give  a  slight  alkaline  reaction.  After  stirring  for 
about  an  hour  the  dyestuff  separates  out,  a  little  salt  being  added  to 
complete  the  precipitation.    The  orange  powder  is  filtered  off  and  dried. 

Dyes  wool  orange  from  an  acid  bath.    (J.  S.  C.  I.,  6,  591.) 

If  a-naphthol  is  used  in  place  of  ^-naphthol,  the  dyestuff  formed  is 
Orange  I.    (J.  S.  C.  I.,  6,  591.) 

so«h/    \n  =  n/  Noh. 


2.  Di-  and  Tri-Aryl  Methane  Dyes. 

These  dyes  may  be  regarded  as  derivatives  of 

C6H5  C6H5 

CH2  and     CH— C6H5 

C6H5  C6H5 
Diphenylme  thane.  Triphenylmethane. 

The  dyes  are  obtained  from  their  amido  and  alkylamido  derivatives, 
these  groups  being  usually  present  in  the  _p-position. 


DYES 


375 


Preparation  386. — Auramine. 

NH2  CI 

(CH3)2N<^_  _\— C— <^       \n.(CH3)2.       C17H22N3C1.  303-5. 

242  gms.  pure  dimethyl  aniline  are  mixed  with  140  c.cs.  water  and 
260  gms.  cone,  hydrochloric  acid,  and  heated  to  30°.  60  gms.  40% 
formaldehyde  are  then  added,  and  the  mixture  heated  to  85°,  with 
occasional  stirring,  for  5  hours.  The  base  is  then  precipitated  by  adding 
120  gms.  sodium  carbonate  dissolved  in  a  little  water.  The  product, 
tetramethyl-diamino-diphenylmethane,  is  filtered  after  cooling  to  20°, 
and  washed  with  water.  It  is  dried  at  50°.  The  yield  of  this  base  is 
almost  quantitative.  127  gms.  diamino  base,  32  gms.  sulphur,  70  gms. 
ammonium  chloride,  and  1,000  gms.  common  salt  are  heated  in  an  auto- 
clave with  stirrer  and  exit  tube  to  110°.  The  substances  should  all  be 
finely  powdered,  and  absolutely  dry.  The  temperature  is  raised  to  130° 
during  2  hours,  and  a  rapid  stream  of  dry  ammonia  passed  through.  At 
140°  a  vigorous  evolution  of  hydrogen  sulphide  begins,  which  lasts  from 
5 — 7  hours,  according  to  the  speed  of  the  stream  of  ammonia.  The  tem- 
perature is  raised  to  145°  during  5  hours,  stirring  being  continued.  The 
ammonia  stream  should  pass  at  a  speed  of  about  5  bubbles  per  second,  and 
it  is  advisable  to  have  a  slight  excess  pressure  of  ^  atm.  measured  by  a 
manometer,  which  can  be  conveniently  done  by  throttling  the  exit  tube. 

When  the  evolution  of  hydrogen  sulphide  has  ceased,  the  contents  of 
the  autoclave  are  placed  in  a  large  basin  and  treated  with  3  litres  of  water 
to  dissolve  out  the  salt.  The  dye  is  then  filtered  off,  and  dissolved  in 
1 J  litres  of  water  at  60°.  The  solution  is  filtered,  and  a  litre  of  saturated 
salt  solution  added,  when  the  auramine  comes  down  in  glistening,  golden 
leaflets.    It  is  filtered  and  dried. 

_^>N(CH3)2.HC1  +  CH20  ->  (CH3)2N<^  \_CH2— (  )>N(CH3)2 

NH2 

■  +  S  +  NH4C1  +  NH3  ->  (CH3)2N<^      )>— C-<^  )>N(CH3)2. 

di 

Yield  —  Up  to  175  gms.    Dyes  cotton  mordanted  with  tannin  or  tartar 
emetic  a  pure  yellow.    (B.,  33,  318.) 
Preparation  387. — Magenta. 

 CH3 

\nh2 

C9nH,nN,CL  337-5. 


7  gms.  aniline  and  27  gms.  commercial  toluidine  (containing  64%  ortho,, 
and  36%  para)  are  heated  with  34  gms.  cone,  hydrochloric  acid  to  130'' 


376  SYSTEMATIC  ORGANIC  CHEMISTRY 


in  a  250-c.c.  flask.  3  gms.  aniline,  13  gms.  commercial  toluidine,  and 
27-5  gms.  nitrobenzene  are  then  added.  The  flask  is  transferred  to  an 
oil  bath  at  100°,  and  1-5  gms.  iron  powder  dissolved  in  the  minimum 
quantity  of  hydrochloric  acid  (2  mols.)  slowly  added.  An  air  condenser 
is  attached,  and  the  temperature  raised  to  180°,  and  maintained  at 
this  temperature  for  about  5  hours.  When  a  sample,  withdrawn  on 
&  glass  rod,  solidifies  on  cooling,  the  action  is  finished.  The  mixture 
is  then  steam-distilled  to  remove  the  nitrobenzene  and  \excess  amines. 
The  melt  is  then  poured  into  250  c.cs.  boiling  water,) with  stirring, 
and  6  c.cs.  cone,  hydrochloric  acid  added  slowly.  As  s$on  as  an  acid 
reaction  is  obtained,  13  gms.  common  salt  are  added,  and  tne  whole 
boiled  for  a  few  minutes.  The  aqueous  solution  (containing  the  hydro- 
chlorides of  aniline  and  toluidine)  is  poured  off  and  the  residue  allowed  to 
cool,  when  it  solidifies  to  a  green  mass.  This  mass  is  broken  up  and 
extracted  with  750  c.cs.  boiling  water  containing  6  c.cs.  cone,  hydrochloric 
acid,  which  dissolves  the  magenta.  The  solution  is  filtered  hot,  and, 
after  cooling  to  60°,  is  again  filtered.  The  magenta  is  then  "  salted  out  " 
with  common  salt,  and  after  standing  some  time,  is  filtered  off  and 
recrystallised  from  water  containing  a  little  hydrochloric  acid. 

The  hydrochloride  forms  green,  glistening  crystals,  giving  a  red  solution 
in  water.    It  dyes  silk  and  wool  bluish-red,  and  mordanted  cotton. 

/  \  C6H5N02  /  v 

CH3/  )NH2  +  02  OHC<^  )>NH2. 

A       CH3  CH3 

,  W     Vh2  /  \nil 


NH/       ^CH  O  C1I  (  \7NH, 


>NH, 

\  / 

Leuco  base. 


CH3 
>H2 


O  /  HC1 


HO.C—   >      ~"  \  / 

Carbinol  base. 


C  (  \NH2 

NHo.Cl. 


\NH2  Magenta. 


is  also  formed. 


\  )=  NH2.C1 
Para-rosaniline  chloride. 


(J.  S.  C.  I.,  5,  163;  7,  118.) 


DYES 


377 


Peeparation  388. — Malachite  Green. 


>N(GH3) 


C  C23II25N2C1.  364-5. 

>:  N(CH3)2C1. 


Method  I. — 50  gms.  of  dimethylaniline,  20  gms.  of  benzaldehyde  and 
20  gms.  of  pulverised  anhydrous  zinc  chloride  (see  p.  506)  are  heated  in  a 
porcelain  dish,  with  frequent  stirring,  on  a  water  bath  for  4  hours.  The 
mass  is  then  melted  by  the  addition  of  hot  water  and  transferred  to  a  large 
flask,  where  it  is  steam-distilled  until  no  more  dimethylaniline  passes  over. 
The  leuco-base  of  the  dye  remains  in  a  viscous  form  on  the  sides  of  the 
flask  after  cooling  ;  the  aqueous  solution  is  decanted  and  the  base  washed 
a  few  times  by  decantation  with  cold  water.  The  base  is  dissolved  in 
boiling  alcohol,  the  solution  filtered  hot,  and  the  filtrate  left  overnight  in 
an  ice  chest.  Colourless  crystals  separate,  which  are  collected  and  dried 
in  air  on  filter  paper.  A  second  crop  may  be  obtained  by  concentrating 
the  mother  liquor.  If  the  base  separates  as  an  oil,  instead  of  crystals, 
more  alcohol  should  be  added,  and  heat  applied  until  the  oil  redissolves. 

A  small  portion  of  the  leuco-base  is  weighed,  dried  at  100°,  and  weighed 
again  in  order  to  determine  its  moisture  content.  The  equivalent  of 
10  parts  by  weight  of  the  anhydrous  base  is  dissolved  by  heating  with  a 
quantity  of  dilute  hydrochloric  acid,  corresponding  to  2-7  parts  by  weight 
of  hydrogen  chloride.  The  colourless  solution  of  the  leuco-base  is  diluted 
in  a  large  beaker  with  800  parts  of  water,  and  10  parts  of  40%  acetic  acid 
added.  The  solution  is  cooled  to  about  0°  by  the  addition  of  lumps  of 
ice,  and  a  freshly  prepared  lead  dioxide  paste  (for  preparation  and  estima- 
tion, see  p.  504),  corresponding  to  7-5  parts  Pb02,  added  gradually  during 
the  course  of  10  minutes,  the  mixture  being  stirred  and  cooled  during  the 
addition.  Stirring  is  continued  for  2  hours,  after  which  the  unchanged 
lead  peroxide  is  filtered  off,  and  the  lead  in  the  filtrate  precipitated  by 
the  addition  of  10  parts  of  sodium  sulphate  dissolved  in  50  parts  of  water. 
Lead  sulphate  is  filtered  off,  the  filtrate  is  heated  to  boiling,  and  15  gms. 
of  sodium  chloride  added  for  each  100  c.cs.  of  dye  solution  ;  while  still 
hot,  8  parts  of  zinc  chloride,  dissolved  in  a  small  quantity  of  water,  are 
also  added.  On  cooling,  the  zinc  chloride  double  salt  of  the  dye  is  filtered 
off,  washed  with  saturated  sodium  chloride  solution,  and  dried  on  a  porous 
plate.  If  the  mother  liquors  are  coloured,  owing  to  some  of  the  dye  still 
remaining  in  solution,  a  further  crop  may  be  obtained  by  adding  more 
sodium  chloride  and  zinc  chloride. 

C6H5CHO  +  2C6H5N(CH3)2  ->  C6H5CH{C6H4N(CH3)2}2  +  H20 

(Leuco  base) 
\0 

/C6H4N(CH3)2  HCl 

C6H5-C/  +  H20  <  C6H5C(OH){C6H4N(CH3)2}2 

V6H4  =  N(CH3)2C1  (Carbinol  base.) 

Malachite  green  hydrochloride. 


378  SYSTEMATIC  ORGANIC  CHEMISTRY 


The  formula  of  the  zinc  chloride  double  salt  is — 
2C23H25N2C1  +  2ZnCl2  +  H20. 

Brass  yellow  prismatic  needles  ;  soluble  in  hot  water  to  a  bluish-green 
solution  ;  dyes  silk,  wool,  jute  and  leather,  a  bluish-green  directly,  and 
cotton  which  has  been  previously  mordanted  with  tannin  and  tartar  emetic. 

Method  II. — 50  gms.  dimethylaniline,  20  gms.  benzaldehyde,  and 
45  gms.  of  cone,  hydrochloric  acid  are  placed  in  a  flask  fitted  to  a  reflux 
condenser,  and  the  mixture  heated  at  100°  for  24  hours.  The  product  is 
then  made  alkaline  with  caustic  soda,  and  steam-distilled  to  remove 
traces  of  benzaldehyde  and  dimethylaniline.  After  this  the  procedure 
is  the  same  as  in  Method  I.    (J.  S.  C.  I.,  6,  433.) 

3.  Pyrone  or  Phthalein  Dyes. 

Preparation  389. — Eosin. 


Na 


Bl'\    A     //\  /Br. 


COONa. 


C20H6O5Br4Na2.  692. 


Into  a  mixture  of  15  gms.  of  fluorescein  and  60  gms.  of  alcohol  (about 
95%),  contained  in  a  flask,  are  added  with  frequent  shaking  11  c.cs.  of 
bromine,  drop  by  drop,  from  a  burette.  When  half  the  bromine  has  been 
added  the  dibromide  which  is  then  formed  is  in  solution  ;  on  further 
addition  of  bromine  the  tetrabromide  separates  out  in  the  form  of  brick- 
red  leaflets.  After  all  the  bromine  has  been  added,  the  mixture  is  allowed 
to  stand  for  2  hours.  The  precipitate  is  filtered  off,  washed  first  with 
alcohol,  then  with  water,  and  converted  into  the  sodium  salt  by  mixing 
with  a  little  hot  water,  carefully  neutralising  with  caustic  soda  (avoiding 
excess),  and  evaporating  to  dryness  on  a  water  bath. 

Bluish-red  crystals  or  brownish-red  powder.  In  water,  bluish-red 
solution ;  dilute  solution  has  green  fluorescence.  In  alcohol,  easily 
soluble,  with  bluish-red  colour  and  yellowish-green  fluorescence.  Dyes 
wool  and  silk  yellowish-red.    (J.  S.  C.  L,  1893,  513.) 

Preparation  390. — Fluorescein. 

HQ/  V     V  ^OH 


DYES 


379 


A  mixture  of  15  gms.  of  phthalic  anhydride  and  22  gms.  of  resorcinol 
is  ground  in  a  mortar.  It  is  then  transferred  to  a  nickel  or  cast-iron 
vessel,  and  heated  in  an  oil  bath  to  180°.  At  this  temperature  7  gms. 
of  powdered  fused  zinc  chloride  (see  p.  506)  are  added,  with  stirring, 
during  the  course  of  10  minutes.  The  temperature  is  raised  to  210°,  and 
maintained  at  this  point  until  the  liquid,  which  gradually  thickens, 
becomes  solid,  for  which  1 — 2  hours  are  required.  The  cold  melt  is 
removed  from  the  vessel  with  a  knife  or  chisel,  powdered,  and  boiled 
10  minutes  with  200  c.cs.  of  water  and  10  c.cs.  of  cone,  hydrochloric  acid. 
This  treatment  causes  the  solution  of  zinc  oxide  and  basic  zinc  chloride. 
The  fluorescein  is  filtered  off,  washed  with  water  until  the  nitrate  no 
longer  shows  an  acid  reaction  ;  it  is  dried  on  a  water  bath. 

Yield. — Almost  theoretical  (32  gms.).  Red  powder  ;  slightly  soluble 
in  water  ;  soluble  in  alcohol ;  soluble  in  alkalies  with  intense  green 
fluorescence  ;  dyes  animal  fibres  a  fast  vellow. 

OH 


II 


OH 


>  .CO  _j_ 

/ 

0' 


CO- 


OH 
OH 

rA  \oh 


A 


,0 


CO 


\0  +  2H20. 

p>  Free  acid. 

^OH 
|2NaOH 
ONa 


K 


Sodium  salt. 


(J.  S.  C.  I,  22,  513.) 


COONa 


'sO 


4.  Nitro  Dyes. 


Preparation  391.— Naphthol  Yellow  S.  (2 : 4-Dinitro-l-naphthoI-7 
sulphonic  acid  (K  Salt) ). 


OK 


SO„K. 


NO. 


C10H4O8N2SK2.  390. 


NO? 


100  gms.  of  cone,  sulphuric  acid  are  warmed  to  100°  in  a  small  flask. 
50  gms.  of  powdered  a-naphthol  are  added  in  one  instalment.  The 
mixture  is  raised  to  120°  by  heating  in  an  oil  or  sand  bath  and  maintained 
at  this  temperature  for  3 — 4  hours.  The  sulphonation  mixture  is  then 
poured  into  600  c.cs.  of  water,  which  are  stirred  mechanically.  When  the 
temperature  of  the  mixture  falls  to  30°  it  is  poured  into  a  mixture  of 
23  gms.  of  cone,  nitric  acid  and  8  c.cs.  of  water,  which  is  well  stirred 
mechanically  ;  the  temperature  is  kept  below  35°  by  cooling  in  water, 


380  SYSTEMATIC  OKGANIC  CHEMISTRY 


if  necessary.  A  further  21  gms.  of  cone,  nitric  acid  are  added  at  such  a 
rate  that  the  temperature  does  not  rise  above  40°.  The  nitration  mixture 
is  filtered  through  woollen  cloth  and  washed  free  from  acid  with  10% 
sodium  chloride  solution.  The  drained  precipitate  is  stirred  with  200  c.cs. 
of  hot  water  at  80°,  solid  sodium  carbonate  added  until  neutral,  and 
the  dyestuff  precipitated  by  adding  20  gms.  potassium  chloride. 
OH  OH 


+  2HN03  +  H2S04 


S03H 


+  3H20. 


N02      (Free  acid). 
Orange-yellow  powder  ;  dyes  wool  and  silk  from  an  acid  bath.    (A.,  152, 
299.) 

5.  Thiazine  Dyes. 
Peeparation  392. — Methylene  Blue  (Hydrated  zinc  double  chloride 
of  tetramethyl-diamido-phenazthionium) . 


N(CH3) 


,  ZnCL.HoO. 


Nitroso-dimethyl-aniline. — 16  gms.  of  dimethylaniline  are  dissolved  in 
53  gms.  of  cone,  hydrochloric  acid  (30%)  and  100  gms.  ice  added. 
10-5  gms.  of  sodium  nitrite  previously  dissolved  in  40  c.cs.  water  are  then 
slowly  run  in  from  a  dropping- funnel,  the  solution  being  agitated  during 
the  addition.  The  temperature  must  be  kept  below  5°  by  the  addition 
of  ice,  when  necessary.  When  the  nitrite  is  added,  the  agitation  is 
stopped,  and  a  test  for  the  presence  of  free  nitrous  acid  applied.  A 
sample  of  the  liquor  is  withdrawn,  diluted  with  3  times  its  volume  of 
water,  and  tested  with  starch-iodide  paper.  If  test  does  not  indicate  free 
nitrous  acid,  more  nitrite  must  be  added  until  a  positive  indication  is 
obtained.  The  solution  should  be  acid  to  Congo  paper,  and  of  a  yellow 
colour  ;  if  not  acid  it  is  somewhat  green.  After  the  addition  of  all  the 
nitrite  the  mixture  is  allowed  to  stand  for  2  hours,  and  at  the  end  of  this 
time  it  should  just  give  a  slight  indication  of  free  nitrous  acid.  The 
greater  part  of  the  nitroso-dimethylaniline  hydrochloride  separates  out  as 
yellow  crystals. 

^-Amino-dimethylaniline. — The  above  mixture  is  well  agitated,  100c.es. 
of  water  and  70  gms.  of  cone,  hydrochloric  acid  added  ;  this  is  followed 
by  20  gms.  iron  filings,  and  sufficient  ice  added  from  time  to  time  to  keep 
the  temperature  below  30°.  The  reduction  is  complete  when  a  drop 
spotted  on  filter  paper  is  quite  colourless.  The  liquor,  which  is  generally 
acid,  is  treated  with  lime-paste  until  it  is  only  faintly  acid  to  Congo  paper  ; 
the  neutralisation  is  completed  by  the  addition  of  chalk  until  frothing 
stops.  The  residue  of  iron  and  chalk  is  filtered  off  and  washed,  the  washings 
being  added  to  the  nitrate. 


DYES 


381 


Thiosulphonic  Acid  and  Dye. — Before  entering  on  this  stage  of  the 
preparation  the  following  solutions  are  prepared  : — 

Solution  I.— 33-5  gms.  sodium  thiosulphate  in  40  c.cs.  water.— 

Solution  II. — 26-4  gms.  sodium  bichromate  in  40  c.cs.  water. 

Solution  III. — 14  gms.  dimethylaniline  in  24  gms.  cone,  hydrochloric 
acids. 

Solution  IV. — 26-4  gms.  sodium  bichromate  in  40  c.cs.  water. 

Solution  V. — 1-5  gms.  copper  sulphate  in  20  c.cs.  water. 

The  clear  neutral  solution  of  ^-amino-dimethylaniline  is  vigorously 
agitated.  Solution  I.  is  added  all  at  once,  and  immediately  following  it 
Solution  II.  during  the  course  of  2  minutes.  After  an  interval  of 
2  minutes  Solution  III.  is  added  all  at  once,  and  immediately  following 
it  Solution  IV.  during  the  course  of  2  minutes.  Agitation  is  continued 
for  7  minutes  before  Solution  V.  is  added.  The  mixture  is  then 
transferred  to  a  large  vessel  and  heated  ;  it  soon  assumes  a  bronze 
appearance,  and  much  frothing  takes  place.  Heat  is  withdrawn  until 
the  froth  settles  ;  when  this  occurs,  the  mixture  is  heated  up  again  and 
filtered  almost  boiling.  The  black  precipitate  of  chromium  hydroxide 
is  washed  with  boiling  water  until  the  filtrate  is  only  faintly  coloured. 
The  total  filtrate  is  heated  almost  to  boiling,  then  treated  with  150  gms. 
common  salt,  40  gms.  of  50%  zinc  chloride  solution  and  10  gms.  cone, 
hydrochloric  acid.  On  cooling,  the  double  zinc  salt  of  methylene  blue 
separates  out  as  a  coppery  powder,  which  is  filtered  off  and  washed  with 
a  little  10%  brine  solution  ;  it  is  dried  at  a  temperature  not  exceeding  50°, 
a  yield  of  about  30  gms.  being  obtained. 

If  "  zinc-free  "  methylene  blue  is  desired,  the  nitrate  from  the  chromium 
hydroxide  is  heated  to  80°,  15  gms.  of  common  salt  added  for  each  100  c.cs. 
of  solution,  also  10  c.cs.  of  cone,  hydrochloric  acid.  On  cooling,  the 
"  zinc-free  "  methylene  blue  separates  in  fine  crystals. 

/\no  /Nneu 


(CH3)2N, 
Dimethylaniline. 


-NIL 


(CH3)2N! 

j?-Nitroso- 
dimethyianiline. 


(CH3)2N 


(CH3)2n! 


(CH3)2N^ 

p  -Amino  - 
dimethylaniline. 


N(CH< 


SO?H 
Thiosulphonic  acid  of 
p  -  amino  -  dimethylaniline . 


S03H 
Thiosulphonic  acid  of 
Bindschedler's  Green, 
N 


(A.,  251,  1.) 


(CH3)2NX/)^g/lxyN(CE 

k 

Methylene  Blue. 


382 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Methylene  blue  is  of  a  very  pure  shade,  and  is  much  used  for  dyeing 
tannined  cotton ;  the  "  zinc-free  "  dye  is  used  for  medicinal  purposes, 
and  also  for  the  production  of  discharge  effects  in  silk  printing. 

Preparation  393 —Methylene  Green  (Nitro-methylene  blue). 

30  gms.  methylene  blue  (Zn  salt)  are  made  into  a  paste  with  35  c.cs. 
water  and  16  gms.  of  60%  nitric  acid  ;  to  this  are  added  at  25°  3-5  gms. 
of  sodium  nitrite  dissolved  in  the  minimum  quantity  of  water.  The 
temperature  is  raised  slowly  to  50°  (rate  1°  per  minute)  with  good  agitation, 
and  kept  there  for  2  hours.  160  gms.  of  saturated  brine  are  then  added, 
and  the  precipitate  filtered  off  after  12  hours.  The  product  is  purified 
by  dissolving  in  800  c.cs.  water  at  60°,  filtering  to  remove  residue,  and 
reprecipitating  the  dye  with  105  gms.  common  salt  along  with  35  gms. 
of  50%  zinc  chloride  solution.  After  standing  for  12  hours,  the  dye  is 
filtered  off,  pressed,  and  dried  at  45°. 

Yield—  About  25  gms.  Used  in  conjunction  with  iron-mordanted 
logwood,  or  with  tin  phosphate  for  dyeing  black  on  silk,  also  for  cotton 
and  calico  printing.    (E.P.,  8992  (1886).) 

Preparation  394. — Primuline. 


I       ySv  /SOaNa 

CfiHo/  >C.CfiH; 


C28H1703N4S4Na.  608. 


6XX3< 


20  gms.  £>-toluidine  and  14  gms.  sulphur  are  well  mixed  together  and 
heated  in  a  jar  in  an  oil  bath  to  250°  C.  The  mass  turns  yellow,  and  the 
reaction  is  finished  when  no  more  H2S  is  evolved. 

The  mass,  after  cooling,  is  powdered  and  heated  with  4  times  its  weight 
of  fuming  sulphuric  acid  (30%  S03)  to  70° — 80°  C.  for  a  few  minutes 
until  a  sample  dissolves  in  caustic  soda.  The  sulphonation  mixture  is 
poured  into  ice-water,  and  the  sulphonic  acid  of  the  primuline  base 
which  is  precipitated  filtered  and  washed  free  of  acid. 

The  paste  is  stirred  up  with  dilute  ammonia  until  alkaline,  filtered 
and  washed  with  cold  water.  The  residue  is  the  ammonium  salt  of 
dehydro-thio-j9-toluidine  sulphonic  acid,  and  the  filtrate  contains  the 
primuline.  The  filtrate  is  saturated  with  common  salt,  when  the  primuline 
separates  out  and  is  filtered  and  dried. 

Dyes  cotton  direct  from  alkaline  or  neutral  bath  primrose-yellow  (see 
Preparation  300).    (D.R.P.,  56606.) 

6.  Indigoid  Dyes. 

Preparation  395. — Indigo. 


>C  =  C(          I      I       C16H10O2N2.  262. 


-CO  v  /  CO- 

>C  =  C< 
-NH/  \NH- 

14  gms.  anthranilic  acid  are  suspended  in  50  c.cs.  benzene.    7  gms. 


DYES 


383 


finely  powdered  potassium  cyanide  are  added,  and  after  shaking, 
7-5  c.cs.  of  40%  formaldehyde.  The  temperature  rises,  and  the  potas- 
sium salt  of  co-cyanmethyl  anthranilic  acid  is  formed  in  the  aqueous 
liquid. 

The  benzene  is  removed,  and  20  c.cs.  of  40%  caustic  soda  solution  are 
added.  The  mixture  is  carefully  heated  over  a  wlregauze  until  ammonia 
begins  to  be  evolved.  After  the  reaction  has  subsided,  heating  is  con- 
tinued until  all  the  ammonia  is  driven  off,  water  being  added,  if  neces- 
sary, to  prevent  the  contents  of  the  flask  becoming  solid.  The  mix- 
ture, when  cold,  is  carefully  neutralised  with  cone,  hydrochloric  acid 
(/using  ph^noljo]^  and  then  acidified  with  about 

15  cxsT^FgE^aTacetic Tacid.  The  yellowish- white  precipitate  of  phenyl- 
glycine-o-carboxylic  acid  is  filtered  off,  washed  with  water,  and  dried  on  a 
porousplate. 

10  parts  of  phenylglycine-o-carboxylic  acid,  or  the  corresponding 
amount  of  the  sodium  or  potassium  salt,  are  added  to  a  solution  of  10 — -12 
parts  of  pure  caustic  soda  in  4 — 6  parts  of  water.  The  mixture  is  then 
quickly  evaporated,  being  stirred  continuously  until  dry.  It  is  powdered, 
and  added  to  8^=J^aTts_ol^solio^^  The 
mixture  is  heated  to  250° — 270°,  and  stirred  with  the  thermometer,  steam 
being  evolved.  The  end  of  the  reaction  is  indicated  by  the  strong  yellow 
colour  of  the  fusion.  The  homogeneous  paste  is  cooled,  and  boiled  with 
water  containing  a  little  sodium  hydrosulphite  to  prevent  oxidation.  The 
liquid  is  filtered  from  paraffin,  and  oxidisj^byjiajssing  air,  when  indigo 
is  precipitated  as  a  dark  blue  powder. 


/\NH2 
LoOH 


NH.CH2CN 
COOK 


/\NH.CH2CN 


COOH 


2NaOH 


/\NH.CH2.COONa 


+  NH3. 


COONa 


/\NHCBLCOONa 


COONa 


/\NH- 
NaOH  _>    |      |  C1F 
-C(ONa)' 

Sodium  indoxyl. 


>CH  +  O, 


-C(ONa)' 


-NH  >  NH 

-CO x  xCO- 


Indigo  dissolves  in  reducing  agents  to  give  a  colourless  leuco-compound. 
Cotton,  wool  and  silk  are  dyed  by  soaki  ig  in  the  leuco-compound  and 
exposing  to  air.    (D.K.P.,  125916.) 


384  SYSTEMATIC  ORGANIC  CHEMISTRY 


7.  Anthraqtuinone  Dyes. 
Preparation  396. — Algol  Yellow. 

C6H5CONH^  CO  NH.COC6H5 

ill!  C28H1804N2. 
CO 


446. 


7  gms.  of  1.8-dinitro-anthraquinone  (Preparation  231)  are  added  to  a 
solution  of  35  gms.  sodium  sulphide  (Na2S.9H20)  in  200  c.cs.  water,  and 
heated  gradually  to  boiling.  The  mass  becomes  dark  blue  and  thick, 
owing  to  the  separation  of  sulphur  and  diamino-anthraquinone.  The 
precipitate  is  filtered  off  and  extra  yield  recovered  by  adding  common  salt 
to  the  filtrate. 

The  diamino  compound  is  then  extracted  from  the  precipitate  by 
boiling  up  with  alcohol  and  filtering  from  sulphur.  The  diamine  is 
precipitated  from  the  alcoholic  solution  by  adding  water.  It  is  filtered 
and  dried  on  the  water  bath. 

Scarlet  red  powder  ;  M.P.  262°  C. 

Benzoylation. — 1  gm.  of  the  diamino  compound  is  treated  with  4  gms. 
benzoyl  chloride  and  10  gms.  dimethylaniline  and  boiled  for  1  hour,  when 
the  benzoyl  derivative  separates  out  as  a  yellow-brown  powder.  The 
unchanged  base  and  the  dimethylaniline  are  extracted  with  dilute 
hydrochloric  acid.    It  is  then  filtered. 

Yellowish  powder  ;  M.P.  234°  C. 

Preparation  397. — Alizarin. 

/COx  /OH(l) 
C6H4\       /C6H2\        ,         C14H804.  240. 
xCOx  xOH(2) 

100  gms.  100%  /?-anthraquinone  sulphonate  (silver  salt)  (see  p.  307) 
are  mixed  with  260  gms.  100%  caustic  soda,  28  gms.  sodium  chlorate,  and 
sufficient  water  to  make  volume  up  to  670  c.cs.  The  mixture  is  placed 
in  an  autoclave  and  heated  up  to  185°  with  continuous  stirring,  the 
pressure  attaining  5 — 6  atms.  After  48  hours,  the  melt  is  allowed 
to  cool,  and  the  following  test  applied  :  2  c.cs.  of  the  melt  are  treated  with 
sufficient  cone,  hydrochloric  acid  to  precipitate  the  alizarin.  The  nitrate 
is  then  extracted  twice  with  a  little  ether  to  remove  traces  of  alizarin. 
The  liquid  is  now  diluted  to  15  c.cs.,  and  the  fluorescence,  which  is  due  to 
unchanged  silver  salt,  and  the  mono-hydroxy-sulpho  acid  observed.  If 
the  reaction  is  complete,  only  a  very  faint  fluorescence  should  develop. 
If  the  reaction  is  not  complete,  the  mixture  is  heated  up  again  in 
the  autoclave  to  190°  for  24  hours.  It  is  then  diluted  with  2  litres  of 
water,  and  the  alizarin  precipitated  at  the  boil  with  50%  sulphuric  acid. 
It  is  cooled  to  50°,  filtered  and  washed.  It  is  not  dried,  as  when  once  dry 
it  no  longer  dyes  properly. 


DYES 


385 


CO  OH 


;SO,H 


NaOH 

To! 


;OH 


CO 


Yield. — About  70  gms.  A  polygenetic  dyestuff,  i.e.,  dyes  mordanted 
cotton  various  colours,  depending  on  the  mordant  used,  e.g.,  iron  oxide 
gives  a  violet  colour,  alumina  a  red  colour,  chromium  a  brown  colour, 
etc.    (J.  S.  C.  I.,  2,  213  ;  E.P.,  1948  (1869).) 

Prepaeation  398. — Anthracene  Brown  (Anthragallol).  1.2.3-Tri- 
hydroxy  Anthraquinone. 


C14H80, 


256. 


36  gms.  pure  benzoic  acid  are  dissolved  in  300  gms.  sulphuric  acid  (mono- 
hydrate)  in  a  glass  or  porcelain  beaker  with  good  stirring.  The  mixture  is 
heated  slowly  to  90°,  at  which  temperature  50  gms.  pure,  dry  gallic  acid  * 
(dried  at  110°)  are  added  in  small  portions  during  an  hour.  The  tempera- 
ture is  then  raised  to  118°,  and  kept  there  for  6  hours,  after  which  the 
melt  is  allowed  to  drop  cautiously  into  a  litre  of  boiling  water,  with  con- 
tinuous stirring.  The  product  is  filtered  boiling  through  a  hot  filter,  and 
the  dye  well  washed  with  hot  water.  The  excess  benzoic  acid  crystallises 
out  in  the  mother  liquor. 

OH  nn  OH 

I  J  COOhI  JoH  \  J\       J\  /OH 

Yield. — 70—80%  theoretical  (70 — 80  gms.).  Dyes  wool  brown  with 
chrome  mordants,  chromium  fluoride  giving  the  best  shades.  (J.  S.  C.  L, 
3,  141.) 


*  Good  quality  gallic  acid  may  be  obtained  by  hydrolysing  tannin  with 
40%  caustic  soda  solution  at  70°  with  the  addition  of  a  little  sodium 
bisulphite  to  protect  the  acid  from  oxidation.  The  gallic  acid  is  then 
precipitated  by  cone,  hydrochloric  acid  and  crystallised  from  water.  (Note. — 
Sulphuric  acid  must  not  be  used.) 


s.o.c. 


CHAPTER  XXVII 


DRUGS 

Preparation  399. — Chloral  Formamide  (Chloralamide). 

CCl3.CH(OH)NH.CHO.       C3H402NC13.  192-5. 

74  gms.  freshly  distilled  chloral  are  added,  with,  stirring,  to  22-5  gms. 
cooled  formamide  (see  Preparation  265).  Much  heat  is  evolved,  and  the 
mixture  sets  on  cooling  to  a  crystalline  mass  of  chloral  formamide.  It  is 
purified  by  recrystallisation  from  dilute  alcohol,  the  solution  not  being 
heated  above  48°  (see  below). 

CCI3CHO  +  HCONH2    ->  CCl3CH(OH).NH.CHO. 

Colourless  crystals  ;  M.P.  114° — 115°  ;  a  hypnotic  ;  above  48°,  is 
reconverted  to  chloral  and  formamide.  (D.R.P.,  50586  ;  E.P.,  7391 
(1886).) 

Preparation  400. — Aspirin  (Acetyl  Salicylic  Acid). 

y.cocHg 

C9H804.  180. 

COOH. 

100  gms.  acetyl  chloride  in  25  gms.  glacial  acetic  acid  are  added  to 
69  gms.  salicylic  acid  in  a  retort.  The  retort  is  gently  heated  until  the 
reaction  commences,  when  heating  is  discontinued.  Hydrochloric  acid 
is  evolved,  and  acetyl  chloride  commences  to  pass  over.  When  the 
reaction  slackens,  the  temperature  is  raised  gradually  to  60°,  and  when  the 
action  has  ceased,  to  70°,  to  remove  acetyl  chloride  as  far  as  possible. 
This  can  be  much  facilitated  by  the  application  of  a  slight  vacuum. 
When  the  distillation  has  ceased  the  contents  of  the  retort  are  poured 
into  an  enamelled  basin  and  allowed  to  crystallise.  The  crystals  are  then 
filtered  off,  washed  with  water,  and  dried  at  30° — 40°.  They  are 
recrystalhsed  by  dissolving  in  ethyl  alcohol  at  about  40°,  and  throwing 
out  of  solution  by  the  addition  of  cold  water. 


\COOH[2]  \COOH  [2] 

Rhombic  plates  ;  M.P.,  which  varies  according  to  rate  of  heating,  is 
given  by  British  Pharmacopoeia  as  134° — 135°  ;  should  give  no  violet 
coloration  with  ferric  chloride  ;  the  most  important  analgesic  and  anti- 
pyretic.   (BL,  1915,  17,  186.) 

386 


OH    [1]  /OCOCH3[l] 


DRUGS 


387 


Peeparation  401. — Chloramine  T. 

CH3.C6H4S02N.NaCl  +  H20.       C7H903NClSNa.  245-5. 

jt?-Toluene-sulphonyl  chloride  (see  Preparation  285)  is  treated  with 
4  times  its  weight  of  dilute  ammonia  solution,  and  stirred  for  several 
hours,  until  all  the  powdered  sulphonyl  chloride  is  converted  into  the 
crystalline  sulphonamide.  A  little  of  the  mixture  is  filtered,  and  the 
crystals  boiled  with  water.  When  no  acidity  is  developed  the  reaction  is 
complete.  The  crystals  are  then  filtered  off,  washed  with  a  little  water, 
and  recrystaliised  from  a  small  quantity  of  water.    Needles  ;  M.P.  64°. 

CH3C6H4S02C1    ->  CH3C6H4S02NH2. 

171  parts  of  _p-sulphonamide  are  treated  with  525  parts  of  a  2N  solution 
of  sodium  hypochlorite  (see  p.  508)  containing  40  parts  NaOH.  A  white 
precipitate  is  immediately  formed,  which,  on  heating  and  subsequent 
cooling,  deposits  crystals  of  Chloramine  T,  which  are  washed  with  brine 
and  recrystaliised  from  water. 

CH3C6H4S02NH2  +  NaOCl    ->  CH3C6H4S02N.NaCl. 

Colourless  needles  ;  a  very  powerful  disinfectant.  (J.  S.  C.  I.,  1918, 
37,288.) 

Preparation  402. — Arsanilic  Acid  (^-Amino-phenylarsinic  acid). 

NH2 

C6H803NAs.  217. 

AsO(OH)2. 

100  c.cs.  arsenic  acid  (technical— 76%)  are  heated  for  12 — 15  hours  at 
140°,  to  concentrate  to  100%.  It  is  then  cooled,  and  into  it  are  stirred 
140  c.cs.  of  dry  ice-cold  aniline.  Aniline  arsenate  is  formed,  which  is 
ground  up  and  heated  to  160°  until  molten,  then  under  a  reflux  con- 
denser for  1—1-1  hours  at  160°— 170°,  and  then  for  1  hour  at  180°— 185°. 
It  is  allowed  to  cool  somewhat,  and  45  c.cs.  N.  caustic  soda  solution 
added  to  decompose  any  arsenate  still  remaining.  The  aniline  liberated 
is  separated  by  extraction  with  ether.  The  aqueous  layer  is  shaken  up 
with  Kieselguhr  or  animal  charcoal,  and  the  arsenilic  acid  precipitated 
from  the  clear  solution  by  adding  a  sufficient  quantity  of  dilute  hydro- 
chloric acid.    It  is  then  filtered  and  washed  with  cold  water. 

NH,~~|(H3As04)a  NH2  NH2 

->    2.        j  + 

\/ 

AsO(OH)2 
Of.  Sulphanilic  acid. 

The  sodium  salt,  NH2.C6H4.AsO(OH)(ONa)  +  5H20,  prepared  by 
neutralising  1  mol.  of  the  acid  with  1  mol.  caustic  soda,  is  known  as 
"  Atoxyl."    (Am.  Soc,  41,  451.) 


388  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  403— Antipyrine,  Phenazone  (l-Phenyl-2*3-Dimethyl 
Pyrazolone). 


CH3.C  =  CH 

„  L  I 


CO        CH^ON,.  188. 


N 
C6H5 

Phenylmethyl  pyrazolone  (see  Preparation  249)  is  methylated  with  a 
methyl  alcoholic  solution  of  methyl  chloride  or  bromide  at  90° — 100°,  a 
slight  excess  of  methylating  agent  being  employed.  The  methylation  can 
be  conveniently  carried  out  in  an  autoclave  fitted  with  an  agitator.  The 
alcohol  is  distilled  off,  and  the  reaction  product  dissolved  in  water 
made  slightly  alkaline  with  caustic  soda.  The  antipyrine  is  then  extracted 
with  benzene,  and  crystallised  from  benzene,  and  finally  from  water, 
animal  charcoal  being  used  to  decolorise. 

CH3C  =  CH— CO               CH3C  =  CH — CO 
HN  N.C6H5  CH3N  N.C6H5. 

White  crystalline  scales ;  M.P.  113°  ;  odourless ;  possesses  bitter 
taste  ;  a  valuable  analgesic  and  antipyretic.    (D.R.P.,  69883,  26429.) 

Preparation  404. — Veronal,  Barbitone  (Diethyl-malonyl  urea,  diethyl- 
barbituric  acid). 

yCO— NHV 

(C2H5)2C<  >CO.       C8H12N203.  184. 

\CO— NH/ 

16  gms.  sodium  are  dissolved  in  300  gms.  absolute  alcohol.  To  the  cooled 
solution  are  added  20  gms.  dry  urea  and  50  gms.  diethyl  malonic  ester 
(see  Preparation  199).  The  mixture  is  heated  in  an  autoclave  for  4 — 5 
hours  at  100°— 110°.  On  cooling,  the  sodium  salt  of  diethyl  barbituric 
acid  separates,  is  filtered  off,  dissolved  in  water,  and  the  free  acid  precipi- 
tated by  the  addition  of  hydrochloric  acid.  The  acid  is  filtered  and 
recrystallised  from  water,  using  animal  charcoal  if  necessary. 

/COOC2H5      NH2X  .CO— NHX 

(C2H5)2C<  +        >CO    _>    (C2H5)2C<  >CO. 

\COOC2H5      NH/  \CO— NH/ 

Colourless  crystals  ;  M.P.  191°  ;  an  important  hypnotic.  (D.R.P.,  146496  ; 
Am.  Soc,  40,  725.) 
Preparation  405. — Sulphonal  (Diethyl-sulphone-dimethyl-methane). 

C2H5S02\  ..CH3 

>C<  C7H1604S2.  228. 

C2H5S02/  \CH3 

1.  Acetone  Ethyl  Mercaptol. — 50  gms.  ethyl  mercaptan  (see  Preparation 
305)  are  added  to  20  gms.  acetone  and  6  gms.  anhydrous  calcium 
chloride.    Dry  hydrochloric  acid  gas  is  passed  in,  the  temperature  being 


DRUGS 


389 


kept  below  25°  by  external  cooling.  When  saturated  with  HC1  the 
mixture  is  allowed  to  stand  overnight,  and  washed  with  water.  The 
layer  of  mercaptol  is  separated  and  dried  over  calcium  chloride,  and 
fractionally  distilled.  Unchanged  ethyl  mercaptan  passes  over  first,  and 
then  the  mercaptol  at  190°. 

2C2H5SH  +  OC.(CH3)2  (C2H5S)2C(CH3)2  +  H20. 

2.  Sulphonal. — 33  gms.  acetone  ethyl  mercaptol  are  added  with  brisk 
agitation  to  1  litre  of  5%  potassium  permanganate  solution.  The 
mixture  gradually  warms  up  as  oxidation  proceeds.  About  85  gms. 
solid  permanganate  are  gradually  added  at  intervals.  Stirring  is  continued 
until  the  permanganate  is  reduced,  when  the  solution  is  boiled  and 
decolorised  with  animal  charcoal.  Sulphonal  separates  out  on  cooling, 
is  filtered,  and  recrystallised  from  aqueous  alcohol. 

(C2H5S)2.C(CH3)2    _>  (C2H5S02)2.C.(CH3)2. 

Colourless,  odourless,  tasteless,  prismatic  crystals  ;   M.P.  125-5°  ;  a 
hypnotic.    (B.,  19,  280.) 
Preparation  406. — Phenacetin  (Aceto-^-phenetidine). 

C2H50^       ^NH.COCHg.       C10H13O2N.  179. 


(1)  .  13-7  gms.  ^-phenetidine  (see  Preparation  367)  are  dissolved  in 
200  c.cs.  water  and  37-5  gms.  20%  hydrochloric  acid,  and  diazotised 
below  6°  with  6-3  gms.  sodium  nitrite.  The  diazo  solution  is  then  run 
into  a  solution  of  9-5  gms.  phenol  in  350  c.cs.  of  2%  sodium  carbonate 
solution.  The  azo  compound  separates  out  in  about  1  hour,  and  is  filtered 
off  and  dried. 

C2H60<^~     \NH2  ->  C2H50<^       \n  =  NCI  -> 
CaH50<^"     ^>N  =  NN/  ^OH. 
Yield.— Theoretical.    M.P.  104-5°. 

(2)  .  24  gms.  of  the  azo  compound  are  dissolved  in  100  c.cs.  alcohol  and 
4  gms.  caustic  soda.  The  solution  is  then  placed  in  an  enamel-lined 
autoclave,  7  gms.  ethyl  chloride  are  added,  and  the  whole  is  heated  under 
pressure  for  5 — 6  hours  at  90° — 100°.  On  cooling,  the  diethoxyl  azo 
compound  separates,  and  is  filtered  off  (M.P.  156°). 

C2H50<^       ^>N  =  ~~yOH  ^C2H50<^  ~^>N  =  N</  ^>OC2H5. 

(3)  .  10  gms.  of  the  diethoxy  azo  compound  are  mixed  with  50  gms.  20  % 
hydrochloric  acid,  and  6  gms.  of  granulated  tin  are  added.  When  all  has 
gone  into  solution,  caustic  soda  solution  is  added  to  make  alkaline,  and  the 
p-phenetidine  distilled  over  by  superheated  steam  at  160° — 180°. 

C2H50/       ^>N      N<^       )>OC2H5  ->  2.C2H50<^  ^NH, 

2  mols.  of  ^9-phenetidine  are  thus  prepared  from  the  initial  1  mol.  of 
j9-phenetidine.    (D.R.P.,  48453.) 


390  SYSTEMATIC  ORGANIC  CHEMISTKY 


(4).  Equal  weights  of  distilled  ^-phenetidine  and  glacial  acetic  acid  are 
heated  under  a  reflux  with  the  addition  of  a  little  fused  sodium  acetate 
until  no  free  base  remains  (test  with  alkaline  ^-naphthol  solution).  The 
excess  of  acetic  acid  is  then  removed  by  distillation  in  vacuo,  and  the 
residue  dissolved  in  boiling  water  to  which  animal  charcoal  is  added, 
and  after  cooling  and  filtering,  phenacetin  separates  out.  It  is  filtered, 
washed,  and  recrystallised  from  water  or  60%  alcohol,  a  little  sulphur 
dioxide  solution  being  added  to  prevent  oxidation. 

C2H50<f       NnH2  ->  C2H50<^  ^NH.COCHg. 


White  glistening  scales  ;  M.P.  134°  ;  a  very  important  analgesic  and 
antipyretic.    (D.R.P.,  139568.) 


CHAPTER  XXVIII 


ELECTEOLYTIC  PREPARATIONS 

Preparation  407. — Benzaldehyde. 

C6H5.CHO.  106. 

The  apparatus  for  this  preparation  consists  of  a  narrow  glass  beaker, 
or  a  wide-mouthed  bottle.  The  beaker  is  corked,  and  an  efficient  glass 
stirrer  passing  through  the  centre  is  attached  to  a  small  turbine  or 
motor.  Four  electrodes  are  fixed  in  position  so  that  they  are  clear  of  the 
stirrer.  Two  anodes,  each  of  sheet  platinum  of  about  1  sq.  dcm. 
surface,  are  placed  diametrically  opposite  one  another,  while  the  two 
cathodes,  spirals  of  platinum  wire  and  each  of  2  cms.  surface,  are  placed 
between  them  near  the  sides  of  the  beaker.  50  gms.  toluene,  200  c.cs. 
of  10%  sulphuric  acid  and  250  c.cs.  of  acetone  are  placed  in  the  cell,  which 
is  surrounded  by  cold  water.  The  current  density  should  be  1-5 — 2 
amperes,  the  E.M.F.  5—6  volts,  and  the  temperature  under  20°.  3The 
stirring  must  be  vigorous  to  keep  the  mixture  in  a  thorough  emulsion. 

From  the  equation 

C6H5.CH3  +  20  =  C6H5.CHO  +  H20 

50  gms.  of  toluene  require  58  ampere  hours,  but  in  order  to  ensure 
complete  oxidation  65  ampere  hours  should  be  passed.  The  contents 
are  then  transferred  to  a  flask,  and  made  slightly  alkaline  with  sodium 
carbonate.  The  acetone  is  removed  by  distillation,  and  the  residue 
steam  distilled,  when  benzaldehyde  and  unchanged  toluene  pass  over. 
Benzaldehyde  is  separated  as  its  bisulphite  compound,  formed  by  shaking 
up  with  sodium  bisulphite,  allowing  to  stand  to  crystallise  and  filtering. 
Dilute  caustic  soda  is  then  added,  the  benzaldehyde  separated  by  steam 
distillation,  dried,  and  redistilled. 

Yield. — 7 — 8  gms.  (see  p.  219).  The  procedure  for  o-  and  ^-xylene  is 
similar.    (Am.  Soc,  22,  723.) 

Preparation  408. — Iodoform  (Tri-iod  Methane). 

CHI3.  394. 

20  gms.  of  anhydrous  sodium  carbonate  and  20  gms.  (8  mols.)  of 
potassium  iodide  are  dissolved  in  20  c.cs.  of  water,  50  c.cs.  (excess)  of 
absolute  alcohol  added,  and  the  whole  poured  into  a  beaker.  The  anode 
is  a  sheet  of  platinum  foil,  8  by  10  cms.,  the  cathode  of  platinum  wire 
wound  into  a  spiral  of  1  cm.  diameter. 

The  solution  is  warmed  to  60°  or  70°,  and  a  current  of  3  amperes 
per  sq.  dcm.,  counting  both  sides  of  the  anode,  is  passed  through  the 

391 


392 


SYSTEMATIC  ORGANIC  CHEMISTRY 


solution,  while  carbon  dioxide  is  bubbled  into  the  liquid  to  neutralise  the 
caustic  potash  formed.  After  1  hour  the  iodoform  which  has  separated 
is  filtered  off  and  washed  with  cold  water. 

2KI  +  H20  +  C02  ->  KaCOs  +  H2  +  I2. 

I2  3I2 
CH3CH2OH   >  CH3CHO   >  CI3CHO  ->  CHI3. 

Yield. — 75%    theoretical.    Yellow   crystals ;  insoluble    in    water ; 

soluble  in  alcohol  and  ether  ;  volatile  in  steam  ;  M.P.  119°.  (C,  1897, 
IL,  .695.) 

Preparation  409. — Methyl  Alcohol. 

CH3OH.  32. 

A  solution  in  500  c.cs.  water  is  made  from  110  gms.  potassium  acetate, 
26  gms.  potassium  carbonate  and  28  gms.  potassium  bicarbonate,  and 
poured  into  a  lead  cell  or  glass  beaker,  which  need  contain  no  anode 
chamber.  The  beaker  should  be  placed  in  a  basin  of  cold  water,  and  the 
cathode  should  take  the  form  of  a  thin  lead  pipe,  with  a  copper  connection 
soldered  to  it,  wound  in  the  form  of  a  coil,  and  placed  close  to  the  inner 
walls  of  the  beaker.  Through  this  pipe  a  supply  of  cold  water  is  run, 
so  that  the  temperature  is  maintained  at  25° — 30°  during  the  electrolysis. 
The  anode  is  of  platinum,  and  should  be  so  arranged  that  it  can  be 
rotated.  The  current  densitv  is  20 — 25  amperes  per  sq.  dcm.,  and  the 
E.M.F.  7—8  volts. 

As  the  electrolysis  proceeds,  acetic  acid  is  dropped  in  at  such  a  speed 
that  the  solution  does  not  become  acid.  When  50 — 60  ampere  hours 
have  passed  the  electrolysis  is  stopped.  The  contents  of  the  cell  are 
then  distilled  to  remove  the  methyl  alcohol,  and  some  formaldehyde, 
which  is  also  produced.  The  alcohol  is  dried  and  redistilled  in  the  usual 
way. 

CH3COO-1-  +  OH'  ->  CH3OH  +  C02 

Yield.— 50— 60%  theoretical  (see  p.  206).    (A.,  323,  304.) 
Preparation  410. — j9-Phenylene-Diamine. 

H2N.C6H4.NH2.  108. 

20  gms.  ^-nitraniline  are  dissolved  in  150  c.cs.  of  alcohol,  and  to  this 
is  added  a  solution  of  5  gms.  sodium  acetate  in  100  c.cs.  hot  water.  This 
mixture  is  then  placed  in  a  beaker,  which  acts  as  a  cathode  cell.  The 
anode  cell,  which  is  a  porous  pot,  contains  a  20%  solution  of  sodium 
carbonate.    The  cathode  and  the  anode  are  both  of  nickel  gauze. 

The  mixture  is  first  warmed  to  75°,  and  the  high  current  keeps  it 
boiling.  Alcohol  may  be  added  from  time  to  time  to  replace  that  evapo- 
rated. The  current  density  is  15  amperes,  and  the  E.M.F.  7 — 8  volts. 
After  about  20  ampere  hours  have  passed,  the  current  density  is  cut  down 
to  2  amperes.  After  24  ampere  hours  have  passed,  the  current  is  stopped  ; 
the  hot  cathode  liquid  is  then  poured  into  a  mixture  of  50  c.cs.  of  sulphuric 


ELECTROLYTIC  PREPARATIONS 


393 


acid  and  100  c.cs.  of  water,  and  allowed  to  stand.  The  j9-phenylene  diamine 
sulphate  is  filtered  and  dried  on  a  porous  plate. 

Yield. — 75%  theoretical  (20  gms.).  o-Nitraniline  gives  by  same  method 
o-phenylene  diamine  ;  m-nitraniline  gives  by  same  method  m-diamido- 
azo-benzene.    (B.,  28,  2350.) 

Pkepakation  411. — Borneol. 

C10H18O.  154. 

A  10%  solution  of  camphor  in  alcohol  and  half  its  volume  of  75% 
sulphuric  acid  is  placed  in  the  cathode  chamber  and  70%  sulphuric  acid 
placed  in  the  anode  chamber.  The  current  density  is  12  amperes,  and 
the  E.M.F.  10 — 15  volts.  The  current  is  allowed  to  pass  for  5  hours, 
the  temperature  being  kept  below  20°.  The  product  is  then  poured  into 
water,  and  the  solid  filtered  off,  dried  and  recrystallised  from  petroleum 
ether 

'  Yield.— 40%  theoretical.    M.  P.  204°— 205°.    (Z.e.,  8,  288.) 
Pkepakation  412. — Di-ethyl  Adipate  (Di-ethyl  ester  ol  hexan  di-acid). 

COOC2H5.(CH2)4.COOC2H5.       C10H18O4.  202. 
Ethyl  Acrylate. 

CH2 :  CH.COOC2H5.       C5H802.  100. 

A  nearly  saturated  solution  of  potassium  ethyl  succinate  (1*5  parts  of 
salt  to  1  part  of  water)  is  placed  in  a  tall  beaker,  which  must  not  be  more 
than  half  full,  and  which  should  be  cooled  in  ice  water.  An  anode  of 
stout  platinum  wire,  made  into  a  spiral,  is  introduced.  The  cathode 
consists  of  a  piece  of  sheet  platinum.  A  current  of  50 — 75  amperes 
per  sq.  dcm.  of  anode  surface  is  then  passed  through.  Much  frothing 
takes  place.  At  the  end  of  the  reaction — 70  c.cs.  of  solution  require 
20  ampere  hours — the  mixture  with  the  adipic  ester  floating  on  the  surface 
is  diluted  with  water  in  a  separating  funnel,  and  extracted  twice  with  ether. 
The  ethereal  extract  is  dried  over  calcium  chloride  and  placed  in  a  distilling 
flask.  After  removing  ether,  the  fraction  distilling  up  to  120°  containing 
ethyl  acrylate  is  separately  collected.  The  residue  containing  diethyl 
adipate  is  distilled  under  reduced  pressure. 

COOC2H5.CH2CII2COOK  COOC2H5.CH2.CH2 

j        ;  '  |      -;-  20()2  -f  2K '". 

COOC2H5.CH2.CH2COO:K  COOC2H5.CH2.CH2 

Yield  of  Diethyl  Adipate.— 30— 35%  theoretical ;  B.P.760  245°  ;  colour- 
less liquid  with  characteristic  odour.  Ethyl  acrylate,  which  is  a  by- 
product, is  only  obtained  in  very  low  vield  ;  B.P.760  101° — 102°. 
(T.  R.  S.  E.,  36,  211.) 


CHAPTER  XXIX 


PRODUCTS  FROM  NATURAL  SOURCES 

Preparation  413. — Quinine  Sulphate. 

80 — 100  gms.  of  powdered  cinchona  bark  are  placed  in  a  mortar 
and  ground  up  with  about  250  c.cs.  of  milk  of  lime.  The  whole  is 
evaporated  to  dryness  on  the  water  bath,  and  the  mass  powdered  up 
when  cold.  This  residue  is  shaken  up  with  about  200  c.cs.  of  chloro- 
form, and  allowed  to  stand  in  a  flask  for  about  12  hours.  It  is  then 
filtered  and  washed  with  chloroform.  The  quinine  is  removed  from  the 
chloroform  extract  by  shaking  up  2  or  3  times  with  dilute  sulphuric  acid 
and  then  with  water,  until  the  aqueous  solution  no  longer  exhibits  a  blue 
fluorescence.  The  acid  and  aqueous  extracts  are  carefully  neutralised 
with  ammonia,  and  the  whole  is  evaporated  on  the  water  bath  until 
quinine  sulphate  begins  to  separate  out;  it  is  filtered  off,  on  cooling. 
Another  crop  of  crystals  may  be  obtained  by  concentrating  the  mother 
liquor.    The  quinine  sulphate  may  be  recrystallised  from  water. 

Yield. — 1 — 2  gms. 

The  free  base  may  be  isolated  by  dissolving  the  sulphate  in  water 
slightly  acidified  with  dilute  sulphuric  acid.  Excess  of  sodium  carbonate 
solution  is  then  added,  when  the  quinine  is  precipitated.  It  is  filtered 
off,  washed  and  dried.    M.P.  175°. 

Preparation  414. — Caffeine  (Theine). 

CH3.N — CO  rn 

CO.C— N<        +  H20.  212. 

I      II  >CH 
CH3N— C— NX 

J  lb.  of  tea  is  boiled  up  with  600  c.cs.  of  water  for  15  minutes,  and 
filtered  through  fine  cotton,  the  leaves  being  washed  with  about  300  c.cs. 
of  boiling  water. 

The  filtrate  is  heated  to  boiling,  and  basic  lead  acetate  (made  by  boiling 
lead  acetate  with  litharge  and  water,  and  filtering)  is  added  until  no  further 
precipitation  of  the  albumens  and  tannins  present  takes  place.  This  is 
filtered  and  the  residue  washed  with  hot  water.  The  lead  in  the  filtrate 
is  precipitated  by  adding  dilute  sulphuric  acid.  The  clear  liquor  is 
decanted  from  the  lead  sulphate,  and  concentrated  to  about  300  c.cs., 
animal  charcoal  being  added.  After  filtering  and  cooling,  the  filtrate  is 
extracted  several  times  with  chloroform.  The  chloroform  is  removed  by 
distillation  on  the  water  bath,  and  the  crude  product  boiled  up  with  water 
and  animal  charcoal,  and  filtered.  The  filtrate  is  then  concentrated  until 
crystallisation  takes  place. 

394 


PRODUCTS  FROM  NATURAL  SOURCES 


395 


Yield. — 1 — 2  gms.    Fine  needles,  containing  1H20  ;  M.P.  132°— 133°. 
Caffeine  may  be  synthesised  from  uric  acid.    (D.R.P.,  121224.) 
Peeparation  415. — D- Alanine  (D-2-Amino-propan  acid). 

CH3.CH(NH2)COOH.       C3H702.N.  89. 

Glycocoll-ester  Hydrochloride  (Hydrochloride  of  ethyl  ester  of  amino 
ethan  acid). 

CH2(NH2.HCl.).COOC2H5.       C4H1002.N.C1.  139-5. 

The  raw  material  employed  is  the  cheap  waste  of  raw  Milan  silk,  500  gms. 
of  which  are  treated  with  2  litres  of  fuming  hydrochloric  acid  (D.  1-19) 
and  frequently  shaken  until,  in  the  course  of  an  hour,  the  threads  have 
fallen  to  pieces.  The  flask  is  warmed,  with  frequent  shaking,  on  a 
steam  bath  ;  the  liquid  foams  considerably,  and  a  dark  violet  solution  is 
produced.  This  is  boiled  under  a  reflux  condenser  for  6  hours  ;  it  is 
advisable  to  add  a  few  gms.  of  animal  charcoal.  When  quite  cold,  the 
acid  liquor  is  filtered  through  a  coarse  but  strong  filtering  cloth,  and 
evaporated  under  reduced  pressure  (10 — 15  mm.)  at  40° — 45°  to  a  thick 
syrup.  This  is  treated  while  still  warm  with  3  litres  of  absolute  alcohol, 
and  a  very  rapid  current  of  dry  hydrogen  chloride  passed  in  without 
cooling  and  with  frequent  shaking,  until  the  liquid  is  saturated.  In  this 
process  complete  solution  must  occur,  and  the  alcohol  must  boil.  The 
operation  is  usually  finished  in  1J  hours.  If  the  current  of  hydrogen 
chloride,  and  consequently  the  rise  in  temperature,  is  too  small,  the 
mixture  must  be  boiled  afterwards  for  \  hour  on  the  water  bath,  in 
order  to  render  the  esterification  as  complete  as  possible. 

The  very  dark  brown  liquid  is  now  cooled  to  0°,  and  "  inoculated  "  with  a 
few  small  crystals  of  glycocoll-ester  hydrochloride,  and  the  greater  part  of 
the  glycocoll-ester  hydrochloride  separates  in  the  course  of  12  hours  at  0° 
in  the  form  of  a  thick  paste  of  crystals.  The  mass  is  filtered  at  the  pump 
through  coarse  linen,  well  pressed,  and  washed  with  a  little  ice-cold 
alcohol.  The  acid  alcoholic  solution  is  evaporated  as  completely  as 
possible  under  low  pressure  from  a  bath  at  40° — 45°,  and  the  residual 
syrup  is  again  esterined  with  \\  litres  of  alcohol  and  hydrogen  chloride, 
as  before.  The  cold  solution  is  "  inoculated,"  and  allowed  to  stand  for  2  days 
at  0°,  when  the,  remainder  of  the  glycocoll  is  for  the  most  part  precipitated 
as  ester  hydrochloride.  The  solution,  after  filtration,  is  again  evaporated 
under  reduced  pressure.  The  syrup  left  behind  contains  the  hydro- 
chlorides of  the  other  amino-acid  esters.  In  order  to  liberate  the  esters, 
the  residue  is  dissolved  by  vigorous  shaking  at  ordinary  temperature  in 
the  smallest  quantity  of  water  (about  \  volume).  To  the  solution  is  added 
about  twice  its  volume  of  ether,  and  the  whole  is  carefully  cooled  in  a 
freezing  mixture.  Strong  caustic  soda  is  then  cautiously  added  until 
the  free  acid  is  almost  neutralised,  and,  finally,  a  saturated  solution  of 
potassium  carbonate.  On  vigorous  shaking,  a  considerable  part  of  the 
liberated  esters  goes  into  solution  in  the  ether.  The  ether  is  now  poured 
off  and  replaced  by  fresh  ether.  The  whole  is  carefully  cooled,  then  an 
excess  of  concentrated  alkali  is  added,  and  immediately  afterwards 


396  SYSTEMATIC  ORGANIC  CHEMISTEY 


potassium  carbonate  in  small  portions,  until  the  whole  mass  has  become 
a  thick  paste.  The  ether  is  repeatedly  renewed  during  the  operation. 
The  extraction  with  ether  is  continued  until  the  extracts  are  colourless. 
This  requires  4 — 5  litres  of  ether. 

The  united  ethereal  solutions,  which  are  brown  in  colour,  are  shaken 
for  5  minutes  with  potassium  carbonate,  then  poured  off,  and  dried  for 
12  hours  over  anhydrous  sodium  sulphate.  When  the  greater  part  of 
the  ether  has  been  evaporated  at  ordinary  pressure  on  a  water  bath,  the 
distillation  is  continued  under  a  pressure  of  10 — 12  mms.  At  ordinary 
temperature,  ether  first  passes  over.  The  distilling  vessel  is  now  warmed 
in  warm  water,  when  a  first  fraction  is  obtained,  which  still  contains 
alcohol  and  ether,  and  also  some  glycocoll  ester  and  alanine  ester.  When 
the  temperature  of  the  bath  has  risen  to  55°,  the  main  part  of  the 
alanine  ester  begins  to  boil.  The  operation  is  discontinued  when,  at  a 
bath  temperature  of  80°,  nothing  more  distils  over.  In  this  way 
110 — 125  gms.  distillate  are  obtained,  consisting  for  the  most  part  of 
alanine  ester. 

To  obtain  free  alanine  the  alanine  ester  is  heated  for  about  6  hours 
with  5  times  its  weight  of  water  on  a  water  bath,  until  the  alkaline  reaction 
has  disappeared.  The  solution  is  evaporated  on  a  water  bath  till 
crystallisation  begins.  The  liquid  is  allowed  to  stand  at  0°,  when  about 
30  gms.  alanine  separate  ;  optical  examination  shows  this  to  consist 
of  almost  pure  ^-compound.  From  the  mother  liquor  a  second  crop  of 
20 — 25  gms.  may  be  obtained,  and  this  still  consists  of  fairly  pure 
active  amino-acid,  so  that  the  total  yields  amount  to  50 — 55  gms.  The 
last  mother  liquor  still  contains  a  fair  amount  of  active  alanine,  but  it  is 
mixed  with  so  much  racemic  substance  that  it  cannot  be  separated  from 
it  by  mere  recrystallisation  from  water.  The  first  two  crops  are  dissolved 
once  more  in  hot  water,  and  the  liquid  evaporated  on  the  water  bath  till 
it  begins  to  crystallise.  At  0°  a  large  quantity  of  the  pure,  active  amino- 
acid  separates  out. 

Glycocoll-ester  hydrochloride :  Colourless  needles  ;  soluble  in  hot  alcohol ; 
very  soluble  in  water  ;  M.P.  144°.  D-alanine :  Needles  ;  soluble  in  water  ; 
decomposes  on  heating  ;  [a]2D°  =  +  9-55°  (HC1).  (J.  pr.,  [2],  37.  160  ; 
B.,  27,  60;  32,2459.) 

Preparation  416.  —  Cystine  (Di-(2-amino-2-carboxyl-ethanyl-(l)  )- 
disulphide). 

HOOC.CH(NH2).CH2Sv 

>       C6H1204N2S2.  240. 
HOOC.CH(NH2).CH2S/ 

500  gms.  of  horsehair  are  boiled  in  a  flask  of  3  litres  capacity 
with  1J  litres  of  cone,  hydrochloric  acid  (about  30%  strength)  for 
6  hours  under  a  reflux  condenser.  The  dark-coloured  liquid  is 
diluted  with  4  litres  of  water,  and,  while  kept  fairly  cool,  is  treated  with 
cone,  potassium  hydroxide  solution  (33%)  until  the  reaction  is  only 
faintly  acid.  To  clarify  the  liquid  it  is  warmed  and  vigorously  stirred 
for  some  time  with  about  40  gms.  of  animal  charcoal,  and  filtered. 


PRODUCTS  FROM  NATURAL  SOURCES 


397 


The  filtrate  is  exactly  neutralised  with  potassium  hydroxide,  and 
set  aside  to  crystallise  at  low  temperature,  preferably  in  the  ice 
chest,  for  5 — 6  days.  The  cystine  which  separates  is  filtered  at  the 
pump,  washed  with,  cold  water,  then  dissolved  in  the  smallest  possible 
quantity  of  warm  10%  ammonia,  again  treated  with  animal  charcoal  in 
the  warm,  and  finally  precipitated  from  the  filtrate  by  the  addition  of 
acetic  acid.  This  operation  is  repeated  once  more  ;  the  final  product  is 
quite  colourless  and  free  from  tyrosine. 

Yield. — 15  gms.  Colourless  crystals.  (E.  Fischer,  "  Organic  Prepara- 
tions," 1908.) 

Peepaeatton  417. — Glucosamine  Hydrochloride  (Hydrochloride  of 
2-amino-tetrol-(3.4.5.6-hexanal-(l) ) ). 

CH2OH.(CHOH)3CH(NH2 :  HCl).CHO.       C6H1305.  165. 

The  carapaces  and  claws  of  lobsters,  which  have  been  cleaned,  as  far 
as  possible  mechanically,  are  digested  for  24  hours  with  cold  dilute 
hydrochloric  acid.  They  may  then  be  cut  up  easily,  and  freed  from 
adherent  fibres  and  flesh.  100  gms.  of  the  material  thus  prepared  are 
covered  in  a  porcelain  dish  with  fuming  hydrochloric  acid,  and  heated 
to  gentle  boiling  on  a  sand  bath.  The  chitin  quickly  goes  into  solution, 
and  the  liquid  becomes  dark  in  colour.  The  liquid  is  evaporated  until 
a  considerable  crystallisation  of  glucosamine  hydrochloride  has  taken 
place,  then  allowed  to  cool,  filtered  at  the  pump  through  linen  or  hardened 
paper,  and  washed  with  a  little  cold  hydrochloric  acid.  The  mother 
liquor,  on  further  evaporation,  yields  a  second  crop  of  crystals.  To 
purify  the  salt  it  is  dissolved  in  warm  water,  and  the  solution  concentrated 
till  crystal] isation  begins. 

Colourless  crystals  ;  soluble  in  hot  water.    (B.,  17,  213.) 

Peeparation  418.  —  Tyrosine  (2-Amino-3-(j9-hydroxyphenyl)-propan 
acid). 

HO.C6H4.CH2.CH(NH2).COOH.       C9HnOs.  167. 

100  gms.  of  silk  waste  are  boiled  for  6  hours  under  a  reflux  condenser 
with  300  c.cs.  of  fuming  hydrochloric  acid  (D.  1-19).  The  greater  part  of 
the  hydrochloric  acid  is  removed  by  evaporating  the  brown-coloured 
solution  under  reduced  pressure  ;  the  residue  is  dissolved  in  water,  filtered, 
and  made  up  to  a  known  volume.  The  percentage  of  hydrochloric  acid 
is  determined  by  titration  of  an  aliquot  part  of  the  liquid,  and  the  amount 
of  sodium  hydroxide  calculated  for  the  whole  solution  is  then  added, 
with  ice  cooling  and  constant  stirring.  A  brownish-black  precipitate 
is  at  once  produced.  After  it  has  stood  for  an  hour  in  ice  water,  it  is 
filtered  ofE  at  the  pump,  dissolved  again  in  hot  water,  and  boiled 
vigorously  with  about  10  gms.  of  animal  charcoal.  The  filtered  liquid 
is  now  colourless,  and  deposits  pure  tyrosine  on  cooling.  By  concentrating 
the  mother  liquor  a  second  crop  of  crystals  may  be  obtained. 

Yield. — 5 — 6  gms.  Colourless  crystals  :  soluble  in  hot  water.  (Z.  ph., 
48,  528.) 


398 


SYSTEMATIC  OKGANIC  CHEMISTKY 


Preparation  419. — Furfurol. 


CH 


CH 


\ 


C5H402. 


96. 


CH\  /C.CHO. 


A  mixture  of  200  gms.  of  bran,  200  gms.  of  cone,  sulphuric  acid,  and 
600  gms.  of  water  is  distilled  from  a  large  flask  till  the  distillate  measures 
about  600  c.cs.  The  latter  is  neutralised  with  caustic  soda,  mixed  with 
150  gms.  of  common  salt  and  again  distilled,  till  about  200  c.cs.  have 
passed  over.  This  distillate  is  again  saturated  with  common  salt, 
extracted  with  ether,  the  extract  dried  over  anhydrous  sodium  sulphate, 
the  ether  removed  on  the  water  bath,  and  the  residue  distilled,  the  fraction 
160° — 165°  being  collected  separately. 

Yield. — 6  gms.  Colourless  liquid  ;  burnt  smell ;  darkens  on  standing  ; 
B.P.  162°.    (A.,  74,  280  ;  116,  258.) 

Preparation  420. — Oleic  Acid  (9-Octadecen  acid). 

CH3(CH2)7CH  =  CH(CH2)7COOH.       C18H3402.  282. 

10  gms.  of  potassium  hydroxide  in  100  c.cs.  of  alcohol  are  heated  with 
30  gms.  olive  oil  for  1 — 2  hours  under  a  reflux.  The  alcohol  is  removed 
on  a  water  bath,  and  dilute  acetic  acid  is  added  to  the  residue 
until  it  is  neutral  to  phenolphthalein.  30  gms.  of  cone,  lead  acetate 
solution  are  then  added,  which  precipitates  a  mixture  of  the  lead  salts 
of  oleic,  palmitic,  and  stearic  acids.  The  mixture  is  filtered  and  washed 
with  alcohol  to  remove  unchanged  oil.  It  is  then  extracted  in  a  Soxhlet 
apparatus  with  ether,  which  dissolves  lead  oleate.  When  the  ether  is 
evaporated  lead  oleate  remains.  Pure  dilute  nitric  acid  is  added,  and 
oleic  acid  separates  as  an  oil.  The  oil  is  removed  by  means  of  a  separating 
funnel,  dried  over  calcium  chloride,  and  distilled  under  reduced  pressure. 


C3H5(O.COC17H33)3  +  3KOH  ->  3C17H33COOK  +  C3H5(OH)3. 

Yield.— 50%  theoretical  (14  gms.).  Colourless  oil ;  M.P.  14°  ;  B.P.10 
223°  ;  decomposes  on  heating  at  ordinary  pressures  ;  D.\5  0-895.  (B.,  27, 
172.) 


CHAPTER  XXX 


STEREOCHEMICAL  REACTIONS 

Preparation  421. — a-Brom-cinnamic  Acid  (3-Phenyl-2-brom-2-propen 
acid)0 

C6H5.CH  :  CBr.COOH.        C9H702Br.  227. 

5  gms.  (1  mol.)  of  pure  a-brom-allocinnamic  acid  are  placed  in  a  test  tube 
with  a  thermometer  immersed  in  the  substance.  The  tube  is  immersed  in 
a  bath  of  cone,  sulphuric  acid  heated  to  200° — 210°,  and  kept  there  for 
10  minutes.  After  cooling,  the  product  is  dissolved  in  dilute  alkali,  and 
after  neutralising  the  excess  of  alkali  the  solution  is  treated  with  a  solution 
of  barium  chloride,  which  precipitates  the  barium  salt  of  a-brom-cinnamic 
acid.    The  free  acid  can  be  liberated  in  the  usual  way. 

C6H5CH  C6H5CH 

ll  ^  II 

Br.C.COOH  COOH.C.Br 
a-Brom-cinnamic  acid.      a-Brom-allocinnamic  acid. 
M.P.  131°.  M.P.  120°. 

Yield. — 80 — 85%   theoretical  (4 — 4-2   gms.).     Colourless  prismatic 
needles  ;  soluble  in  hot  benzene  ;  M.P.  131°.    (J.  C.  S.,  83,  686.) 
Preparation  422. — Mesaconic  Acid  (£mws-3-Carboxy-2-buten  acid). 


CCOOH.       C5H604.  130. 

II 

HOOC.C.H 

20  gms.  of  citraconic  acid  (see  p.  236)  are  dissolved  in  the  minimum 
quantity  (about  25  c.cs.)  of  pure  dry  ether  in  a  quartz  flask.  5  gms.  of 
chloroform  and  a  few  drops  of  a  moderately  strong  solution  of  bromine  in 
chloroform  are  then  added.  The  solution  is  exposed  to  strong  sunlight,  or 
to  the  rays  of  a  mercury  vapour  lamp.  Mesaconic  acid  soon  begins  to 
separate  on  the  side  of  the  flask  nearest  the  light.  The  flask  is  occasion 
ally  turned,  and  drops  of  bromine  are  added  at  intervals  until  no  further 
separation  takes  place.  The  pasty  mass  is  filtered,  washed  with  ether, 
and  dried. 

CH3  CH3 

!  I 
CCOOH        ->  CCOOH 

II  II 
CH.COOH  HOOC.C.H 

Yield. — 73%  of  complete  conversion  (15  gms.).    Colourless  crystals  ; 

399 


400 


SYSTEMATIC  ORGANIC  CHEMISTRY 


M.P.  202°  ;  somewhat  soluble  in  water ;  insoluble  in  ether  and  in 
chloroform.    (A.,  188,  73.) 
Preparation  423. — Benz-^-aldoxime  (/5-Benzaldoxime). 

C6H5CH 

||  C7II7ON.  121. 

N.OH 

12  gms.  a-benzaldoxime  are  dissolved  in  50  c.cs.  pure  anhydrous  ether. 
Dry  hydrogen  chloride  is  passed  into  this  solution,  using  a  rather  wide 
delivery  tube,  since  the  hydrochloride  of  the  /S-oxime,  which  separates 
quickly,  is  liable  to  block  the  end  of  the  tube.  The  precipitate  is  filtered 
off,  washed  with  ether,  transferred  to  a  separating  funnel  and  mixed 
with  50  c.cs.  of  ether.  Cone,  sodium  carbonate  solution  is  then  added, 
with  shaking,  until  effervescence  ceases.  The  ethereal  layer,  which  con- 
tains the  /?-oxime,  is  separated  from  the  lower  aqueous-sodium  chloride 
layer,  dried  over  anhydrous  sodium  sulphate,  and  the  ether  removed  in 
a  vacuum  desiccator.  The  residue  forms  a  mass  of  small  needles,  which 
are  pressed  out  on  a  porous  plate. 

Yield.— Almost  theoretical  (10  gms.).  M.P.  128°— 130°  (on  quick 
heating) .    (B.,  23,  1684.) 

C6H5CH  C6H5.CH 

II  ->  II 

HON  N.OH. 

Preparation  424. — Resolution  of  Inactive  Mandelic  Acid  into  its 
Optically  Active  Components. 

COOH 

I 

H— C— OH.       C8H803.  152. 
I 

CeHs 

20  gms.  (less  than  1  mol.)  of  crystallised  cinchonine,  10  gms.  (1  mol.) 
of  mandelic  acid  (recrystallised  from  benzene)  and  500  c.cs.  of  water  are 
heated  with  agitation  in  a  flask  on  a  boiling  water  bath  for  an  hour. 
After  cooling  to  laboratory  temperature,  the  undissolved  material  is 
filtered  off,  but  not  washed.  The  nitrate  is  left  in  an  ice  chest  to  cool 
to  6° — 8°,  and  then  seeded  with  a  few  crystals  of  ^-cinchonine  mandelate  ; 
if  this  seeding  material  is  not  available,  a  small  quantity  may  be  prepared 
in  one  of  the  following  ways  : — 

1.  The  point  of  a  glass  rod  is  dipped  in  the  filtrate,  then  withdrawn 
and  allowed  to  dry  in  the  air  ;  during  this  slow  evaporation  some  crystals 
of  (Z-cinchonine  mandelate  form  on  the  rod.  The  rod  is  again  immersed 
in  the  cold  solution,  and  occasionally  rubbed  against  the  sides  of  the 
containing  vessel. 

2.  A  few  c.cs.  of  the  filtrate  are  treated  with  saturated  brine  solution 
until  a  slight  precipitation  takes  place,  then  heated  to  redissolve,  and 
finally  left  to  stand  several  days  in  a  cool  place  until  crystals  separate. 
These  crystals  contain  some  e£-cinchonine  mandelate,  and  serve  for 
seeding  material. 


STEREOCHEMICAL  REACTIONS 


401 


After  seeding,  the  nitrate  is  left  for  a  few  days  at  6° — 8°,  until  no  more 
crystals  of  ^-cinchonine-^-mandelate  separate  out.  These  are  filtered 
off,  dried  on  a  porous  plate,  and  the  nitrate  A  reserved  for  the  preparation 
of  Z-mandelic  acid.  When  dry,  the  crystals  are  dissolved  in  25  times 
their  weight  of  water  by  heating  in  a  flask  on  a  boiling  water  bath  for  an 
hour  ;  the  undissolved  portion  is  filtered  off,  but  not  washed  ;  the  nitrate 
is  seeded  with  a  few  crystals  of  cZ-cinchonine-<#-mandelate  (reserved  from 
the  first  product  if  purer  material  is  not  available),  and  left  to  stand  at 
6° — 8°  for  a  few  days  until  no  further  crystallisation  takes  place.  The 
crystals  are  filtered  off,  redissolved  in  30  parts  of  water,  and  the  solution 
treated  with  a  slight  excess  of  ammonia  to  precipitate  the  cinchonine, 
which  is  filtered  off.  The  nitrate  containing  ammonium  e£-mandelate  is 
acidified  with  hydrochloric  acid  and  extracted  with  ether.  The  ether  is 
evaporated  off,  the  residue  is  heated  for  some  time  on  a  water  bath,  and 
then,  after  cooling,  crystals  of  ^-mandelic  acid  separate.  These  are 
pressed  on  a  porous  plate,  and  recrystallised  from  benzene. 

Colourless  needles  ;  M.P.  133° — 134°  ;  easily  soluble  in  hot,  somewhat 
soluble  in  cold  water  ;  [d]%)0  =  +  157°  in  aqueous  solution. 

A  sample  of  mandelic  acid  showing  lsevo-rotation  may  be  obtained 
from  filtrate  A  by  liberating  the  free  acid,  after  the  manner  described 
for  the  d-acid.    (B.,  16,  1773  ;  32,  2385.) 

Pkepakation  425. — Resolution  of  a-Phenylethylamine.    (p.  360.) 

C6H5\ 

>CH.NH2.       C8HnN.  121. 

Commercial  dry  malic  acid  (1  part — 1  mol.)  is  covered  with  4  parts  of 
cold  water  in  a  beaker.  The  quantity  of  racemic  a-phenylethylamine 
(1  mol.)  necessary  to  form  the  acid  salt  is  then  added,  during  a  few  minutes 
with  constant  stirring.  Both  base  and  acid  dissolve,  but  before  the  acid 
has  completely  disappeared  the  solution  becomes  slightly  syrupy,  and  a 
crystalline  powder  begins  to  separate.  The  mass  is  stirred  with  a  glass 
rod  until  the  malic  acid  is  all  dissolved,  and  then  left  to  stand  overnight. 
The  crude  £-malate  of  ^a-phenylethylamine  is  filtered  off  with  suction, 
well  pressed  down,  and  washed  with  a  little  cold  water.  [The  mother 
liquor  A,  containing  chiefly  the  Z-malate  of  I- a-phenylethylamine,  is 
reserved  for  the  preparation  of  the  famine  (see  below).]  The  crude  salt, 
which,  when  dry,  is  approximately  equal  in  weight  to  that  of  the  phenyl - 
ethylamine  used,  is  recrystallised  3  or  4  times  from  water.  The  following 
method  is  convenient  (p.  14)  :  the  crude  salt  is  divided  into  two  portions, 
B  and  C.  B  is  dissolved  in  the  minimum  of  hot  water  on  a  boiling  water 
bath,  filtered  hot,  if  necessary,  and  set  aside  to  crystallise  ;  the  formation  of 
small  crystals  should  be  induced  by  cooling  in  ice  water  and  scratching 
with  a  glass  rod.  When  no  more  crystals  separate,  the  crop  Bx  is  filtered 
off,  and  the  nitrate  and  small  quantity  of  washings  used  to  recrystallise  C 
from  which  crop  Cx  is  obtained.  Bx  is  recrystallised  in  the  minimum  of 
boiling  water,  yielding  crop  B2  and  a  mother  liquor,  which  is  used  to 
recrystallise  Cx.    The  recrystallisation  is  continued  in  this  manner  until 


402 


SYSTEMATIC  ORGANIC  CHEMISTRY 


crops  B4  and  C4  are  obtained.  B4  is  pure  c?-amine-£-malate,  and  is  set 
aside.  The  mother  liquors  from  Cl5  C2,  C3  and  C4,  are  combined  and 
evaporated  to  about  \  of  their  volume,  then  cooled  in  ice  water,  and 
the  resulting  crop  of  crystals  D  filtered  off.  C4  is  recrystallised  once 
more  from  fresh  boiling  water,  and  the  mother  liquor  from  C5  is  used  to 
recrystallise  D.  C5  is  pure,  and  T>1  is  recrystallised  4  more  times  from 
water,  after  which  it  is  pure. 


If  large  quantities  of  salt  are  being  recrystallised,  the  mother  liquors 
of  J)1 — D5  should  be  worked  up  after  the  above  manner  to  yield  more 
^-amine  Z-malate.  The  yield  of  pure  cZ-amine  £-malate  should  be  about 
70%  of  the  crude  product.  The  pure  salt  is  dissolved  in  water,  the  solution 
placed  in  a  separating  funnel,  and  cone,  caustic  soda  solution  added  so 
long  as  any  turbidity  of  the  aqueous  layer  is  produced.  The  upper  layer 
of  base  is  separated,  and  the  lower  aqueous  layer  extracted  with  ether 
to  recover  any  dissolved  base.  The  ethereal  extract  is  united  with  the 
base  and  dried  over  anhydrous  sodium  sulphate.  The  ethereal  solution 
is  introduced,  in  portions  at  a  time,  to  a  Claisen  distilling  flask  of  appro- 
priate size,  and  the  ether  distilled  off  (see  p.  32).  The  residue  is  then 
distilled  in  an  apparatus  filled  with  hydrogen,  the  fraction  180° — 190° 
being  collected.  For  polarimetric  observations  the  amine  should  be 
distilled  directly  into  a  polarimeter  tube,  as  it  is  a  strong  base  which 
absorbs  carbon  dioxide  with  avidity. 

Yield. — 90%  theoretical  (calculated  on  pure  malate),  or  30%  of  the 
weight  of  racemic  base  used. 

In  the  above  resolution  an  equivalent  amount  of  the  carbamate  of  the 
base  can  be  used  in  place  of  the  free  base. 

For  the  isolation  of  the  l-base  the  solution  A  (referred  to  above)  is  treated 
with  an  excess  of  caustic  soda  to  liberate  the  base,  which  is  extracted  with 
ether.  The  ethereal  extract  is  dried  over  anhydrous  sodium  sulphate, 
and  after  the  removal  of  the  ether  the  base  passes  over  at  185° — 190°. 
This  base,  which  is  lasvo-rotatory,  is  treated  with  tartaric  acid,  just  as 
the  racemic  base  was  with  malic  acid,  and  the  pure  ?-base  obtained  after  six 
recrystallisations  of  the  salt. 


a-Phenylethylamine  :  B.P.  186°— 187°  ;«]>=-  +  38-28°  and  [a]D  -  + 
40-27  at  15°.  '  (J.  pr.,  72,  307.) 


B.    Bj^    B2    B3  B4 

C  O2    O3  0  5 


CHAPTER  XXXI 


DECOMPOSITIONS 


Peeparation  426.— Butyric  Acid  (Butan  acid). 

CHs.CH2.CH2.COOH.  C4H802. 


88. 


10  gms.  of  ethyl  malonic  acid  (p.  234)  are  introduced  into  a  small  dis- 
tilling flask,  which  is  placed  in  an  oil  bath  with  the  side  tube  sloping 
upwards.  A  cork,  carrying  a  thermometer  with  bulb  immersed  in  the 
substance,  is  inserted  in  the  neck  of  the  flask.  The  substance  is  heated 
at  180°  until  no  further  carbon  dioxide  is  evolved.  The  side  tube  of  the 
flask  is  then  sloped  downwards  and  the  product  (butyric  acid)  distilled, 
the  fraction  160° — 165°  being  collected. 


CHs.CHaCH(COOH)2  ->  CH2.CH2.CH2.COOH  +  C02. 

Yield.— 85%  theoretical  (5-5  gms.).    Colourless  liquid  ;  rancid  odour  ; 
B.P.  162-3°  ;  D.16[5  0-8141.    (A.,  138,  218  ;  J.,  1868,  514.) 
Preparation  427. — Pyrogallol  (1.2.3-Trihydroxy  benzene). 


10  gms.  of  gallic  acid  and  20  gms.  of  powdered  pumice  are  mixed  and 
placed  in  a  retort.  A  cork,  carrying  a  delivery  tube,  is  inserted  through 
the  tubulus  to  serve  for  the  entrance  of  carbon  dioxide.  The  retort  is 
then  heated  on  a  sand  bath  with  a  stream  of  carbon  dioxide  passing 
through,  the  stem  of  the  retort  sloping  downwards  into  a  receiver.  Crystals 
of  pyrogallol  condense  in  the  stem,  which  should  be  warmed  with  a  small 
flame  to  cause  the  product  to  melt  and  flow  down  into  the  receiver. 


Yield.— 40%  theoretical  (3  gms.).  Colourless  crystals  ;  M.P.  133°  ; 
soluble  in  alcohol,  ether  and  water.    (A.,  101,  48.) 

Preparation  428. — Diethyl  Collidine  Dicarboxylate  (2.4.6 -Trimethyl- 
3.5-dicarbethoxy  pyridine). 


C6H3(OH)3. 


126. 


C6H2(OH)3.COOH 


C6H3(OH)3  +  C02. 


CH3 


C 


C2H5OOC.Ci 


■C.COOC2H5 


C14H1904N. 


265. 


[C.CH 


3 


20  gms.  of  ethyl  dihydrocollidine  dicarboxylate  (see  Preparation  91)  and 

403  d  d  2 


404 


SYSTEMATIC  ORGANIC  CHEMISTRY 


20  gms.  alcohol  are  placed  in  a  small  flask,  which  is  immersed  in  a  bath 
of  cold  water.  Nitrous  fumes  (p.  509)  are  led  into  the  mixture  until  a  test 
sample  dissolves  to  a  clear  solution  in  dilute  hydrochloric  acid.  The 
alcohol  is  then  evaporated  off  on  a  water  bath,  the  residue  treated  with 
sodium  carbonate  until  alkaline,  and  the  oil  which  separates  extracted 
with  ether.  The  ethereal  extract  is  dried  over  potassium  carbonate,  the 
ether  evaporated,  and  the  residue  distilled.  The  fraction  290° — 310°  is 
collected  and  redistilled,  the  pure  ester  distilling  at  308° — 310°. 

C5H2N(CH3)3(COOC2H5)2  +  O       C5N(CH3)3(COOC2H5)2  +  H20. 

Yield.— 80%  theoretical  (16  gms.).  Yellow  oil;  B.P.  308°— 310°. 
(A.,  215,  8.) 

Preparation  429. — Collidine  (2.4.6 -Trimethyl  pyridine). 

 CH3 

CH3<^       ^>N       C8HnN.  121. 
"  CH3 

10  gms.  of  powdered  dry  di-potassium  collidine  dicarboxylate  (see 
Preparation  178)  are  intimately  mixed  with  20  gms.  of  slaked  lime,  and  the 
mixture  introduced  into  a  50-cm.  length  of  combustion  tubing,  closed  at 
one  end.  A  loose  plug  of  asbestos  is  placed  in  the  open  end  of  the  tube, 
the  tube  is  tapped  horizontally  on  the  bench  to  make  a  passage  for  gas 
and  then  connected  by  means  of  an  adapter  to  a  small  receiver.  The 
tube  is  placed  in  a  sloping  combustion  furnace,  so  that  the  sealed  end 
is  slightly  elevated.  The  closed  end  is  first  heated,  the  rest  gradually,, 
and  finally  the  whole  length  is  strongly  heated  with  the  tiles  in  position. 
The  distillate  is  taken  up  with  ether,  the  extract  dried  over  solid 
potassium  hydroxide  and  distilled,  the  fraction  169° — 174°  being  separately 
collected. 

C5N(CH3)3(COOK)2  +  2Ca(OH)2  ->  2CaC03  +  2KOH  +  C5NH2(CH3)3. 

Yield. — Almost  theoretical  (4  gms.).    B.P.   172°  ;  greenish-yellow 
liquid  with  an  obnoxious  odour.    (A.,  215,  32.) 
Preparation  430. — Thiophen  (1.3 - Di-en -1.4- butylene  sulphide). 

CH— CH 

II  II 

CH    CH  C4H4S.  84. 


100  gms.  (less  than  1  mol.)  of  phosphorus  trisulphide  (p.  507)  and 
100  gms.  (1  mol.)  of  thoroughly  dry  sodium  succinate  are  intimately 
mixed  and  placed  in  a  retort,  which  is  of  such  a  size  that  the  mixture 
does  not  more  than  half  fill  it.  The  retort  is  connected  to  a  condenser, 
and  the  latter  passes  through  a  cork  into  a  receiver  cooled  in  a  freezing 
mixture.  A  wash  bottle  containing  dilute  caustic  soda  and  fitted  with  a 
cork  carrying  two  delivery  tubes  is  connected  on  the  one  side  to  the 
receiver,  and  on  the  other  to  a  draught  chamber  (or  a  very  slight  suction 


DECOMPOSITIONS 


405 


from  a  pump).  On  heating  the  retort  gently  with  a  small  flame  a  reaction 
soon  commences,  and  the  mass  swells  up  with  the  evolution  of  much 
sulphuretted  hydrogen.  At  this  stage  the  flame  is  withdrawn  and  the 
reaction  allowed  to  proceed  spontaneously  until  completion  (e.g.,  till  gas 
ceases  to  bubble  through  the  wash  bottle).  The  contents  of  the  receiver 
j  are  distilled  from  a  water  bath,  washed  with  dilute  caustic  soda,  dried 
over  metallic  sodium  and  redistilled. 

(CH2.COONa)2  +  4H2S  ->  C4H4S  +  Na2S  +  2S  +  4H20. 

Yield. — 33%  theoretical  (40  gms.).    Colourless  liquid  ;    faint  smell 
resembling  that  of  benzene  ;  B.P.  84°.    (B.,  18,  454.) 
Preparation  431. — Thioxene  (1. 4-Dimethyl-thiophene). 

CH— CH 

II  II 

(CH3)C      C(CHo)       C6H8S.  118. 

Y 

6  gms.  (1  mol.)  of  acetonyl-acetone  (see  p.  188)  are  heated  with 
4  gms.  (excess)  of  finely  powdered  phosphorus  pentasulphide  in  a  sealed 
tube  at  140° — 150°  for  an  hour.  On  cooling,  a  colourless  liquid  and  a 
solid  are  obtained  ;  the  former  is  poured  off  and  fractionally  distilled. 
The  distillation  is  repeated  over  metallic  sodium,  the  fraction  132° — 136° 
being  retained. 

CH2.CO.CH3  CH  =  C(CH3) 

(  +  P2S5    ^  j  /S. 

CH2.CO.CH3  CH  =  C(CH3) 

Yield. — 50%  theoretical  (3  gms.).  Colourless,  mobile  liquid  ;  charac- 
teristic odour  ;  B.P.  135°  ;  D.1^5  0-9755  ;  gives  a  cherry-red  colour  with 
a  solution  of  isatin  in  concentrated  sulphuric  acid  ;  this  colour  changes 
to  reddish-brown  on  warming.    (B.,  18,  2251  ;  20,  1747.) 

Preparation  432— Phenyl  Isothiocyanate  (Phenyl  mustard  oil). 

C6H5NCS.       C7H5NS.  135. 

64  c.cs.  cone,  hydrochloric  acid  and  20  gms.  thiocarbanilide  are  boiled 
for  30  minutes  in  a  flask  attached  to  a  reflux  condenser,  when  the  phenyl 
isothiocyanate  separates  as  an  oil.  40  c.cs.  water  are  added  and  the  whole 
distilled  until  about  15  c.cs.  remain  in  the  flask.  The  distillate  is  extracted 
with  ether,  which  is  then  dried  with  calcium  chloride.  The  ether  is 
removed  by  distillation,  and  the  fraction  boiling  at  197° — 222°  collected. 
This  is  redistilled,  and  the  fraction  218° — 222°  retained. 

HC1 

(C6H5NH)2CS   >  C6H5NCS  +  C6H5NH2(HC1). 

Yield — 55%  theoretical  (7  gms.).  Colourless  liquid  with  pungent 
odour  ;  B.P.  222°  ;  D  15  5  1-135.    (Z.  Ch.,  1869,  589.) 

Preparation  433. — Trimethylethylene  (2-Methyl-2-buten). 

(CH3)2  :  C  :  CH.CH3.       C5H10.  70. 
20  gms.  (1  mol.)  of  amyl  alcohol  (from  fusel  oil)  are  mixed  with  30  gms. 


406  SYSTEMATIC  OKGANIC  CHEMISTRY 


of  anhydrous  zinc  chloride  in  the  form  of  small  lumps,  left  for  24  hours, 
then  heated  on  a  sand  bath,  the  low-boiling  distillate  being  collected  and 
carefully  fractionated.  The  product  is  a  mixture  of  several  isomeric 
amylenes,  but  consists  mainly  of  tri-methyl-ethyiene. 

(CH3)2 :  C  :  CH.CH3. 

The  receiver  must  be  cooled  in  ice. 

C5HnOH  —  H2O->C5H10. 

Volatile  liquid  ;  B.P.  370°.    (A.,  128,  225.) 

Peepaeation  434. — Citraconic  Anhydride  (Anhydride  of  c^-3-carboxyl- 
2-buten  acid). 

CH3CCO 

J  )>0.       C5H403.  112. 
HCCO 

250  gms.  of  crystallised  citric  acid  are  dehydrated  by  heating  in  a 
porcelain  basin  to  a  temperature  not  exceeding  150°.  When  the  acid 
has  become  fluid  the  whole  is  allowed  to  cool,  removed  from  the  basin 
and  coarsely  powdered.  The  anhydrous  acid  is  then  placed  in  a  retort 
and  rapidly  distilled.  The  distillate  separates  into  two  layers,  the  upper 
layer  consisting  of  water  and  citraconic  acid  and  the  lower  layer  of  impure 
citraconic  anhydride.  The  layers  are  separated  and  the  upper  layer 
fractionated,  the  fraction  190° — 210°  being  collected  and  added  to  the 
anhydride  layer.  This  mixture  is  distilled  under  30  mms.  pressure,  the 
fraction  110° — 114°  being  retained. 

CH2.COOH 

I 

COH.COOH 

I 

CH2.COOH 

7^.-22—25%  theoretical  (30—35  gms.).    Colourless  liquid  :  B.P.30 
110°— 114°  ;  B.P.760  213°— 214°.    (A.,  188,  73.) 
Peepaeation  435. — Ethylene  (Ethen). 

CH2  :  CH2.       C2H4.  28. 

50  c.cs.  of  syrupy  or^o-phosphoric  acid  (D.  1-75)  are  heated  until  a 
thermometer  in  the  liquid  indicates  210°,  and  alcohol  run  in  very  slowly 
by  means  of  a  dropping  funnel  drawn  out  to  a  point  and  reaching  to  the 
bottom  of  the  flask.  During  the  addition  the  temperature  must  be  kept 
between  200°  and  220°.  The  gas  is  dried  by  bubbling  through  cone, 
sulphuric  acid. 

C2H5OH  —  H20  =  C2H4. 

Colourless  gas  with  sweet  smell  ;  sparingly  soluble  in  water,  more 
readily  in  alcohol  and  ether  ;  liquifies  at  10°  and  60  atms.  (P.  C.  S., 
17,  147.) 


CH3 

! 

C.CO         +  C02  +  2H20. 

I  )o 

CHCO 


DECOMPOSITIONS 


407 


Preparation  436— Acetonitrile  (Methyl  cyanide). 

CHgCN.       C2H3N.  41. 

15  gms.  of  phosphorus  pentoxide  are  introduced  into  a  200-c.c.  dis- 
tilling flask  attached  to  a  short  condenser.  As  the  pentoxide  absorbs 
moisture  rapidly  and  becomes  sticky,  it  is  convenient  to  push  the  neck 
of  the  distilling  flask  through  a  cork,  which  fits  the  phosphorus  pentoxide 
bottle,  and  then  to  shake  the  oxide  until  the  required  weight  is  introduced. 
10  gms.  of  powdered  acetamide  are  immediately  introduced,  the  mixture 
shaken  up,  and  distilled  over  a  small  flame,  which  is  constantly  moved 
about.  To  the  distillate  is  added  about  half  its  volume  of  water,  and  then 
solid  potassium  carbonate,  until  no  more  dissolves.  The  upper  layer  of 
liquid,  which  consists  of  methyl  cyanide,  is  separated  and  distilled  over  a 
little  fresh  phosphorus  pentoxide. 

CH3.CO.NH2  —  H20  =  CH3CN. 

Yield. — 70%  theoretical  (5  gms.).  Colourless  liquid  ;  characteristic 
odour  ;  B.P.  82°.    (A.,  64,  333  ;  65,  297.) 

Preparation  437. — Acrolein  (2-Propenal). 

CH2 :  CH.CHO.       C3H40.  56. 

200  gms.  of  glycerine  previously  dehydrated  by  heating  in  an  open 
basin  to  170°  are  mixed  with  400  gms.  of  potassium  bisulphate  broken 
to  the  size  of  small  shot  in  a  glass  flask,  or  better,  a  metallic  retort  of  at 
least  4  litres  capacity.  The  delivery  tube  of  the  retort  is  connected  to  a 
long  condenser  to  the  lower  end  of  which  a  distillation  flask  is  fastened 
on  tightly  (e.g.,  by  means  of  an  adapter). 

This  latter  is  surrounded  by  a  freezing  mixture,  and  its  side  tube  con- 
nected to  a  draught  pipe.  The  whole  apparatus  is  fitted  up  in  a  fume 
cupboard. 

The  mixture  is  allowed  to  stand  in  the  closed  retort  for  several  days, 
and  then  slowly  heated  and  distilled,  a  gas-ring  being  used  to  heat  the 
retort.  Water  first  distils,  then  the  contents  of  the  retort  swell  consider- 
ably, and  acrolein  mixed  with  water  and  sulphurous  acid  passes  over. 
The  distillation  is  continued  till,  after  several  hours,  practically  no  more 
liquid  distils. 

The  distillate  consists  of  two  layers,  the  upper  one  being  acrolein,  the 
lower  an  aqueous  solution  of  sulphur  dioxide.  The  latter  is  removed  by 
shaking  with  powdered  litharge  till  no  more  white  lead  sulphite  is  formed. 
The  whole  mass  is  again  distilled  on  a  water  bath,  the  receiver  being 
cooled,  as  before,  and  the  same  precautions  taken  to  prevent  the  escape 
of  uncondensed  vapours. 

The  distillate  is  dried  over  calcium  chloride  and  again  distilled  on  a 
water  bath.    All  these  operations  must  be  carried  out  in  a  good  fume  cup- 
board, and,  to  prevent  loss  by  polymerisation,  as  quickly  as  possible. 
CH2OH.CHOH.CH2OH  ->  CH2  =  CH.CHO  +  2H20. 

Yield. — 30%  theoretical  (35  gms.).  Colourless  mobile  liquid  ;  pene- 
trating odour  ;  attacks  the  eyes  ;  polymerises  on  keeping  to  a  white  trans- 
lucent solid  (disacryl)  resembling  porcelain  ;  a  small  quantity  of  alkali  or  a 


408  SYSTEMATIC  OKGANIC  CHEMISTRY 


solution  of  potassium  cyanide  brings  about  the  change  in  a  few  minutes  ; 
B.P.  52°.    (BL,  36,  550  ;  A.  Ch.,  [6],  26,  367  ;  A.  SpL,  3, 180  ;  B.,  5,  810.) 
Preparation  438. — Pyruvic  Acid  (2-Oxy-propan  acid). 

CHg.CO.CO.OH.       C3H403.  88. 

200  gms.  of  potassium  hydrogen  sulphate  and  100  gms.  of  tartaric 
acid  are  finely  powdered  and  intimately  mixed.  The  mixture  is  distilled 
in  a  short-necked,  2-litre,  round-bottomed  flask,  attached  to  a  moderately 
long  condenser,  from  a  paraffin  bath  heated  to  220°.  The  apparatus  is 
fitted  up  in  a  fume  cupboard.  The  mass  froths  a  great  deal  at  first,  and  j 
it  is  necessary  to  interrupt  the  heating  when  the  flask  is  half  full  of  froth, 
as  otherwise  it  may  boil  over.  When  the  temperature  of  the  bath  has 
fallen  to  about  120°  the  heating  is  recommenced.  The  distillation  is 
continued  until  no  more  liquid  distils.  The  distillate  is  at  once  fraction- 
ated under  reduced  pressure,  the  fraction  68° — 70°  at  20  mms.  being 
separately  collected.  It  may  also  be  fractionated  at  ordinary  pressures, 
the  fraction  130°— 180°  being  redistilled  and  collected  at  165°— 170°, 
but  it  is  difficult  to  obtain  it  colourless  in  this  way. 

COOH.CH(OH).CH(OH).COOH  =  CH3.CO.COOH  +  H20  +  C02. 

Yield— 30%  theoretical  (20  gms.).  Colourless  liquid  ;  polymerises  on 
keeping  ;  has  a  characteristic  odour  somewhat  resembling  that  of  acetic 
acid  ;  MP.  10°  ;  B.P.20  68°— 70°  ;  B.P.760  165°  ;  K  =  0-56.    (A.,  242,  268.) 

Preparation  439. — Acetaldehyde  (Ethanal). 

CH3.CHO.       C2H40.  44. 

The  apparatus  is  set  up  as  shown  in  sketch  (Fig.  53).  To  the  lj-litre  ,  1 
round-bottomed  flask  is  atttached  a  slanting  condenser  with  a  long 
delivery  tube  dipping  into  30  c.cs.  dry  ether  in  a  flask  surrounded  by 
ice-water,  a  further  delivery  tube  passing  into  a  second  flask  containing 
ether.  A  tap-funnel  is  also  attached  to  the  flask.  100  gms.  (1  mol.) 
potassium  dichromate  (or  an  equivalent  quantity  of  sodium  dichromate) 
and  420  c.cs.  of  water  are  placed  in  the  flask  and  gently  warmed  on  a 
sand  bath.  The  flame  is  removed  and  a  warm  mixture  of  100  gms. 
(excess)  of  absolute  alcohol  and  140  gms.  (1  mol.)  of  cone,  sulphuric  acid 
slowly  run  in  from  the  tap-funnel,  the  flask  being  occasionally  shaken. 
Much  heat  is  evolved,  and  the  alcohol  which  distils  is  returned  by  the 
reflux  condenser.  When  all  the  alcohol-acid  mixture  has  been  added, 
the  flask  is  heated  on  a  sand  bath  and  warm  water  (30°)  is  passed 
through  the  condenser.  The  aldehyde  passes  over  into  the  ether. 
Anhydrous  sodium  sulphate  is  added  to-  the  ethereal  solution,  which  is 
still  kept  in  the  ice-water.  After  a  time  the  solution  is  decanted  and 
the  residue  washed  with  a  little  dry  ether.  The  solutions  are  combined 
and  dry  ammonia  gas  (for  preparation,  see  p.  503)  passed  through  until 
the  solution  is  saturated.  After  standing  for  an  hour,  the  solution 
deposits  crystals,  which  are  filtered  off  and  washed  with  a  little  dry  ether. 
The  yield  of  aldehyde  ammonia  is  about  40%  theoretical,  calculated  on 
the  alcohol  used.  The  crystals  are  dissolved  in  an  equal  weight  of  \ 
water,  and  distilled  on  a  water  bath  with  a  mixture  of  1J  parts  cone. 


DECOMPOSITIONS 


409 


sulphuric  acid  and  2  parts  water,  the  receiver  being  well  cooled  in  a 
freezing  mixture.  The  temperature  of  the  water  bath  is  gradually  raised 
until  the  water  begins  to  boil,  when  the  distillation  is  interrupted.  The 


Fig.  53. 


distillate  is  dried  with  anhydrous  calcium  chloride,  and  redistilled  from 
a  water  bath  heated  to  30°.  The  aldehyde  is  kept  in  a  well-stoppered 
bottle. 

3C2H5OH  +  K2Cr207  +  4H2S04  ->  3CH3.CHO  +  K2S04  + 

Cr2  (S04)3  +  7H20. 
CH3CHO  +  NH3  ->  CH3CH(OH)NH2. 
2CH3CH(OH)NH2  +  H2S04  ->  2CH3CHO  +  (NH4)2S04, 

Yield. — 40%  theoretical  (19  gms.).  Colourless  liquid;  sharp  odour; 
B.P.  21°  ;  J).  I  0-807  ;  miscible  with  water,  alcohol  and  ether.  (A.,  14, 
133  ;  J.  pr.,  [1],  76,  54.) 

For  modifications  of  the  above  method,  see  Am.  Soc.  44,  2658. 

Dehydrogenation  of  Primary  Alcohols  to  Yield  Aldehydes. 

When  ethyl  alcohol  is  passed  over  reduced  copper  at  300° — 400°, 
decomposition  takes  place  into  acetaldehyde  and  hydrogen,  the  reaction 
being  reversible. 

CH3.CH2OH       CH3.CHO  +  H2. 

Methyl  alcohol  as  well  as  the  higher  aliphatic  and  the  aromatic  alcohols 
behave  similarly.  The  copper  acts  catalytically,  and  while  cobalt, 
nickel,  iron,  zinc,  platinum,  also  serve,  copper  is  the  most  suitable. 

At  high  temperatures  two -side  reactions  accompany  the  main  reaction. 


410  SYSTEMATIC  ORGANIC  CHEMISTRY 


1.  The  aldehyde  formed  is  split  up  into  hydrocarbon  and  carbon 
monoxide. 

R.CHO  — >  EH  +  CO. 

2.  Dehydration  of  the  alcohol  takes  place. 

R.CH2.CH2OH  ->  RCH  :  CH2  +  H20. 

The  operation  should,  therefore,  be  conducted  at  the  lowest  temperature 
at  which  dehydrogenation  proceeds.  A  margin  of  20°  above  this  point 
is  generally  not  unfavourable. 

Preparation  440. — Acetaldehyde. 

CH3CHO.       C2H40.  44. 

A  combustion  tube  1  metre  long  is  loosely  packed  for  three-quarters  of 
its  length  with  copper  oxide  (either  small  lumps  or  wire  form),  the  layer 
being  held  in  position  with  loose  asbestos  plugs.  The  tube  is  placed  in  a 
long  cylindrical  air  bath  (Fig.  43)  fitted  with  2  thermometers,  preferably 
nitrogen  filled.  The  oxide  is  reduced  to  metal  by  heating  to  180° — 200° 
in  a  current  of  specially  purified  hydrogen.  The  reduction  occupies  about 
6  days.  The  hydrogen  (from  a  Kipp)  should  be  passed  first  through 
caustic  soda  solution,  then  through  cone,  sulphuric  acid,  then  over  heated 
copper  gauze  or  turnings  (previously  washed  with  alcohol  to  remove 
grease)  to  remove  arsenic,  and  finally  through  a  tower  containing  sticks 
of  caustic  soda.  On  no  account  must  any  part  of  the  apparatus  be  heated 
until  all  air  has  been  expelled  from  the  apparatus. 

When  the  reduction  is  finished,  the  side  tube  of  a  silica  distilling  flask 
is  connected  to  the  combustion  tube,  while  a  dropping  funnel  is  inserted 
through  a  cork  in  the  neck  of  the  flask.  The  other  end  of  the  combustion 
tube  is  connected  first  to  an  empty  flask,  and  then  to  a  worm  condenser, 
which  in  turn  is  connected  to  two  suction  flasks  cooled  in  ice  and  salt. 
The  silica  flask  is  heated  in  an  air  bath  to  300°  while  alcohol  is  dropped  in 
at  a  moderate  rate  from  the  tap-funnel.  At  the  same  time  the  combustion 
tube  is  heated  to  300°  or  even  as  high  as  340°.  The  vapours  from  the 
tube,  after  condensation,  yield  unchanged  alcohol,  a  little  water,  and  up 
to  40%  of  acetaldehyde  ;  the  escaping  hydrogen  is  led  to  a  draught  pipe. 
After  a  time,  when  the  catalyst  begins  to  lose  its  activity,  the  temperature 
of  the  air  bath  is  raised  to  near  400°. 

The  aldehyde  is  separated  from  the  condensed  liquid  by  fractional 
distillation  ;  with  an  efficient  column  two  distillations  should  give  a  pure 
product.  The  recovered  alcohol,  after  treatment  with  alkali  (to  remove 
traces  of  acid  which  always  develop)  and  redistillation,  can  be  again 
passed  over  the  catalyst. 

The  highest  conversion  obtainable  with  one  passage  over  the  catalyst 
is  about  40%,  since  an  equilibrium  results  at  this  stage. 

The  copper  loses  its  activity  after  some  time,  but  is  easily  regenerated 
by  oxidation  in  a  current  of  air  at  300°,  and  subsequent  reduction  with 
hydrogen. 

CH3CH2OH       CH3CHO  +  H2. 

(See  p.  409.) 


DECOMPOSITIONS 


411 


Preparation  441. — Benzil. 

C6H5.COCO.C6H5. 


C14H10O2. 


210. 


20  gms.  of  benzoin  and  50  c.cs.  of  cone,  nitric  acid  (D.  =  1-42)  are 
placed  in  a  large  flask,  which  is  then  heated  on  an  actively  boiling  water 
bath.  A  vigorous  reaction  soon  commences,  and  torrents  of  nitrous 
fumes  are  evolved  at  first  ;  for  this  reason  the  operation  should  be  con- 
ducted in  a  fume  cupboard.  After  2  hours'  heating,  the  product  is  poured 
into  vigorously  stirred  cold  water,  the  crystalline  deposit  filtered  off, 
washed  with  cold  water,  pressed  out  on  filter  paper  and  recrystallised 
from  alcohol. 

C6H5.CO.CH(OH).C6H5  +  0  ->  C6H5CO.CO.C6H5  +  H20. 

Yield. — 80%  theoretical  (16  gms.).  Yellow  prisms  ;  insoluble  in  water  ; 
M.P.  95°    (A.,  34,  188.) 

Preparation  442. — a-Brom-cinnamic  Acid  and  a-Bromallo-cinnamic 
Acid  (Cis-  and  Tm/is-3-phenyl-2-brom-2-propen  acid). 


20  gms.  (1  mol.)  of  cinnamic  acid  dibromide  (p.  332)  are  covered  with 
alcohol  and  the  theoretical  amount  (2  mols.)  of  alcoholic  potash  (say, 
70  gms.  of  a  10%  solution)  added.  After  heating  for  about  15  minutes 
in  a  small  flask,  the  mixture  is  evaporated  to  dryness  in  a  dish  on  a  water 
bath.  The  residue  is  digested  with  an  amount  of  water  sufficient  to 
dissolve  about  3  parts  of  the  potassium  salts,  and  an  excess  of  a  10% 
solution  of  barium  chloride  added.  Barium  a-bromcinnamate  is  precipi- 
tated, while  barium  a-bromallocinnamate  remains  in  solution.  The 
former  is  filtered  off,  washed  with  dilute  barium  chloride  solution,  and  the 
free  acid  precipitated  by  treatment  with  hydrochloric  acid  ;  it  is  filtered 
off,  washed  with  water  and  dried  on  a  porous  plate.  It  is  recrystallised 
from  benzene  as  colourless  prismatic  needles  ;  M.P.  131°  ;  yield  11  gms. 
The  brom-allo-acid  is  recovered  in  a  similar  manner  by  acidifying  the 
solution  containing  it  (as  Ba  salt).  It  is  recrystallised  from  petroleum 
ether  as  prisms  with  a  yellow  tinge  ;  M.P.  120°. 


C6H5CHBr.CHBr.COOH  +  2KOH  ->  C6H5CH  :  CBr.COOK  +  KBr  +  2H20 

(J.  C.  S,  83,  673.) 

Preparation  443.—  Menthene  (l-Methyl-4-(l-methyl  ethyl)-3-cyclo 
hexen). 


C6H5CH  :  CBrCOOH. 


C9H702Br. 


227. 


CH(CH3)2 


C 


HC; 


jCH2 


C10H 


138. 


H2C 


l-CR2 


CH3 

70  gms.  (1  mol.)  of  crude  menthyl  chloride  (p.  327)  are  added  to  a  warm 


412  SYSTEMATIC  ORGANIC  CHEMISTRY 


solution  containing  75  gms.  (excess)  of  caustic  potash  dissolved  in  320  gms. 
of  phenol.  The  mixture  (contained  in  a  flask)  is  maintained  at  150°  for 
10 — 12  minutes,  and  then  distilled  until  the  thermometer  (still  immersed 
in  liquid)  registers  200°.  The  distillate  is  placed  in  a  funnel  and  shaken 
with  dilute  caustic  soda  until  free  from  phenol ;  it  is  then  distilled  over 
sodium,  the  fraction  160° — 170°  being  retained  and  again  distilled  over 
sodium. 

C10H19C1  +  C6H5OK  ->  C10H18  +  C6H5OH  +  KC1. 

Colourless  liquid  ;  B.P.  167°  ;  D.»  0-8064.    (B,  29,  1843.) 
Preparation  444. — Dipentene. 

C_CH<^      ^CCH3.       C10H16.  136. 
<lH3  CH7CH 

10  gms.  (1  mol.)  of  pure  dipentene  hydrochloride  (see  p.  334)  are  care- 
fully heated  with  20  gms.  (excess)  of  aniline  until  the  reaction  commences, 
when  heating  is  continued  for  2 — 3  minutes.  To  the  mixture  is  added 
20  c.cs.  (excess)  of  glacial  acetic  acid,  and  the  excess  of  aniline  removed 
by  steam  distillation.  Oxalic  acid  is  added  to  the  distillate  and  steam 
distillation  again  effected.  The  aqueous  distillate  is  separated,  the  hydro- 
carbon being  dried  over  solid  caustic  potash.  It  is  then  twice  distilled 
over  metallic  sodium. 

-2HC1 
C10H18CI2  >  C10H16. 

Colourless  liquid  ;  B.P.  178°— 180°.  (B.,  40,  603  ;  A.,  245,  196  ; 
350,  150.) 

Preparation  445. — s-Xylenoi  (3. 5-Dimethyl-l- hydroxy  benzene). 

(CH3)2C6H3(OH).       C8H10O.  122. 

10  gms.  of  dimethyl  cyclohexenone  (p.  77)  are  dissolved  in  20  gms.  of 
glacial  acetic  acid,  and  the  solution  cooled  by  ice- water,  care  being  taken 
that  the  acid  does  not  solidify.  A  solution  of  13  gms.  of  bromine  in  10 
gms.  of  glacial  acetic  acid  is  added  slowly  from  a  dropping  funnel  with 
stirring,  and  the  whole  allowed  to  stand  overnight  in  a  draught  cupboard  ; 
hydrobromic  acid  is  evolved.  Next  day  the  solution  is  heated  on  a  water 
bath  to  about  50°  with  frequent  shaking  ;  after  being  a  short  time  at 
this  temperature  the  bath  is  raised  to  boiling,  and  heating  continued 
until  there  is  but  slight  evolution  of  hyplrobromic  acid.  A  reflux  air 
condenser  is  then  attached  and  heating  continued  over  a  wire  gauze 
until  the  acetic  acid  commences  to  boil,  and  until  the  evolution  of  hydro- 
bromic acid  almost  ceases.  The  solution  is  cooled  and  poured  into  a  cold 
solution  of  75  gms.  of  caustic  potash  in  150  c.cs.  of  water.  The  by-products 
insoluble  in  the  potash  solution  are  extracted  with  ether,  and  the  alkaline 
solution  saturated  with  carbon  dioxide  to  liberate  the  xylenol,  which  is 
distilled  off  in  steam  in  presence  of  carbon  dioxide.    The  distillation  is 


DECOMPOSITIONS 


413 


stopped  when  a  test  portion  of  the  distillate  gives  no  precipitate  of  tribrom- 
xylenol  (see  p.  347)  on  the  addition  of  a  few  drops  of  bromine.  The  dis- 
tillate is  left  in  the  ice  chest  overnight,  when  the  greater  part  of  the  xylenol 
crystallises  out ;  this  is  filtered  off.  The  xylenol  in  the  filtrate  is  recovered 
by  saturating  with  common  salt  and  extracting  with  ether. 

CH2 — CO  CH2 — CO 

CH3.CH<f  \cR  +  Br2  ->  CH3.CH<f  \m.Br 


CH2  —  C.CH3  CH2  —  CBr.CH3 

CH2— CO  CH  =  C(OH) 

->  2HBr  +  CH3.c/  \cR  ~>  CH3— c/  ScH 

CH  -  -  C.CH3  CH  —  CXH3. 

Yield. — 60%  theoretical  (6  gms.).    Crystalline  substance  ;  M.P.  64°  ; 
B.P.  760  220°— 221°.    (Bl,  [3J,  11,  702  ;  B.,  18,  362,  2672  ;  20,  410.) 
Preparation  446. — Glutaric  Acid  (Pentan  di-acid). 

COOH.CH2.CH2.CH2.COOH.       C,H804.  132. 

A  mixture  of  20  gms.  of  methylene  dimalonic  ester,  20  gms.  of  cone, 
hydrochloric  acid  and  20  c.cs.  of  water  is  heated  for  6  hours  in  a  flask 
under  reflux.  At  the  end  of  this  time  the  product  is  evaporated  to 
dryness,  and  the  residue  (glutaric  acid)  distilled  under  reduced  pressure  ; 
it  distils  at  185° — 195°  under  10  mms.  pressure.  The  small  quantity  of 
anhydride  formed  is  eliminated  by  warming  with  a  little  water.  After 
drying,  the  product  is  recrystallised  from  benzene. 

CH2{CH(COOC2H5)2}2  ->  COOH.CH2.CH2.CH2.COOH  +  4C2H5OH  +  2C02. 

Yield. — 75%  theoretical  (6  gms.).  Soluble  in  hot  benzene  ;  M.P.  97°. 
(B.,  27,  2346.) 

Preparation  447. — 2.6-Dibromaniline  (2.6-Dibrom-l-amino  benzene). 

C6H3(NH2)Br2.       C6H5NBr2.  251. 

45  gms.  of  cone,  sulphuric  acid,  13  c.cs.  of  water  and  10  gms.  of  dry 
dibromsulphanilic  acid  (p.  342)  are  placed  in  a  flask,  which  is  fitted  with 
a  cork  bored  with  three  holes.  Through  one  hole  a  glass  tube,  sealed 
at  the  lower  end  and  passing  down  into  the  mixture,  is  inserted  ;  inside 
this  tube  a  thermometer  is  placed.  The  other  holes  hold  glass  tubes  to 
convey  superheated  steam  through  the  flask.  The  mixture  is  heated  to 
170°  in  an  oil  bath,  and  superheated  steam  is  blown  through.  The 
temperature  rises  gradually,  but  must  not  be  allowed  to  exceed  180°. 
Some  of  the  dibromaniline  formed  is  carried  over  by  the  steam,  but  most 
of  it  remains  in  the  flask.  After  about  90  minutes,  steam  is  shut  off  and 
the  contents  of  the  flask  poured  into  a  large  volume  of  cold  water.  The 
precipitate  is  filtered  off,  dried  on  filter  paper,  and  recrystallised  from 
petroleum  ether. 

NH2.C6H2Br2S03H  +  H20  ->  NH2C6H3Br2  +  H2S04. 

Yield.— 83%  theoretical  (6  gms.).  Colourless  needles ;  M.P.  83°— 84°. 
(A.,  253,  275.) 


414  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  448. — Benzene  Sulphuric  Acid. 

C6H5.S02H.       C6H602S.  142. 

40  c.cs.  water  are  placed  in  a  300-c.c.  flask  provided  with  a  reflux 
condenser  and  dropping-funnel  and  heated  to  boiling.  10  gms.  of  good 
quality  zinc  dust  are  added,  the  source  of  heat  is  withdrawn,  and  10  gms. 
of  benzenesulphonic  chloride,  in  small  portions  at  a  time,  are  added  from 
the  funnel.  A  vigorous  reaction  follows  each  addition,  and  this  is  allowed 
to  subside  before  more  is  added.  When  all  is  in,  the  flask  is  heated  for  a 
short  time  over  a  small  flame,  then  cooled,  and  the  precipitate  of  zinc 
dust  and  zinc  benzenesulphinate  filtered  off.  The  precipitate  is  then 
mixed  with  a  solution  of  10  gms.  anhydrous  sodium  carbonate  in  50  c.cs. 
of  water,  and  the  whole  heated  for  10  minutes  on  a  boiling  water  bath  ; 
by  this  means  sodium  benzenesulphinate  is  formed  and  goes  into  solution. 
The  precipitate  is  filtered  off.  The  filtrate  is  evaporated  to  half  its  volume, 
then  cooled  and  acidified  with  dilute  sulphuric  acid.  After  standing, 
and  scratching  the  sides  of  the  containing  vessel  with  a  glass  rod,  colourless 
crystals  of  benzenesulphinic  acid  separate.  These  are  filtered  off  and 
recrystallised  from  a  little  water. 

2C6H5S02.C1  +  2Zn  ->  (C6H5S02)2Zn  +  ZnCl2. 

Colourless  crystals  ;  insoluble  in  water  ;  M.P.  83°— 84°.    (B.,  9,  1585.) 


CHAPTER  XXXII 


MISCELLANEOUS  PREPARATIONS 

Preparation  449. — Epichlorhydrin. 

CH2C1CH.CH2.       C3H50C1.  92-5. 

V 

100  gms.  of  glycerine  are  dehydrated  by  heating  on  a  sand  bath  until 
the  temperature  registers  175°.  After  cooling  to  ordinary  temperature, 
it  is  mixed  with  an  equal  volume  of  glacial  acetic  acid.  Dry  hydrogen 
chloride  is  passed  into  the  cold  solution  until  saturated  (2  hours). 
The  mixture  is  heated  on  a  water  bath,  and  after  standing  overnight, 
is  again  treated  with  hydrogen  chloride  for  about  6  hours.  The  liquid  is 
then  distilled.  Hydrochloric  and  acetic  acids  first  pass  over  ;  the  fraction 
160° — 210°,  which  contains  chiefly  dichlorhydrin,  is  separately  collected 
and  used  for  the  next  stage.    (Yield,  about  60  gms.) 

To  the  dichlorhydrin  is  added,  with  constant  stirring,  a  cooled  solution 
of  50  gms.  caustic  potash  in  100  c.cs.  water.  The  temperature  must  not 
be  allowed  to  rise.  The  epichlorhydrin  is  then  extracted  with  ether, 
and  the  ethereal  solution  washed  with  water  in  a  separating  funnel,  and 
dried  over  calcium  chloride.  The  ether  is  removed  on  a  water  bath 
and  the  residue  fractionally  distilled,  using  a  column  (see  p.  21).  The 
fraction  115° — 125°  is  then  collected.  Above  this  temperature  aceto- 
dichlorhydrin  distils. 

CH2OH.CHOH.CH2OH  +  HC1 
CH2Cl.CHOH.CH2OH  +  HC1 
CH2C1CH0HCH2C1  +  KOH 


Yield — 12 — 15%  theoretical  (12 — 15  gms.).    Colourless  mobile  liquid, 
with  ethereal  smell ;  B.P.  117°  ;  D.  1-203.    (A.  Spl.a  1,  221.) 
Preparation  450.— Benzamide. 

C6H5CONH2.       C7H7ON.  121. 

10  gms.  of  benzonitrile  are  mixed  with  150  c.cs.  of  3%  aqueous  hydrogen 
peroxide,  and  about  3  c.cs.  of  2N  caustic  soda  added.  The  mixture  is 
warmed  to  40°,  and  shaken  until  all  the  oil  disappears  and  a  white  solid 

415 


CH2Cl.CHOH.CH2OH  + 
a-Monochlorhydrin. 

CH2C1CH0HCH2C1  +  H. 
aa-Dichlorhydrin. 

CH2CHCH2C1  +  KC1  +  I 


O 

E  pichlorhy  drin . 


416  SYSTEMATIC  ORGANIC  CHEMISTRY 


(benzamide)  is  formed.  The  solid  is  filtered  off,  washed  with  water, 
and  recrystallised  from  alcohol. 

C6H5CN  +  H202  ->  C6H6CONH2  +  0. 

Yield.— Theoretical  (12  gms.).    M.P.  128°.    (B.,  18,  355.) 
Preparation  451.— Cupferron  (NH4  salt  of  nitrosophenylhydroxyl- 
amine). 

.NO 

C6H5N<  C6H902N3.  155. 

\ONH4. 
» 

725  gms.  phenylhydroxylamine,  obtained  from  the  .reduction  of  nitro- 
benzene (see  Preparation  375),  is  treated  with  3  litres  ether.  The  ether 
insoluble  material  (sodium  chloride)  is  filtered  off  and  weighed,  this  weight 
being  deducted  from  the  weight  of  crude  phenylhydroxylamine.  The 
filtrate  is  placed  in  a  5-litre  round-bottomed  flask,  cooled  to  0°,  and  stirred 
with  an  efficient  mechanical  stirrer,  while  a  rapid  stream  of  ammonia  gas  is 
passed  into  the  solution.  After  about  15  minutes  the  theoretical  quantity 
of  freshly-distilled  amyl  nitrite  (107  gms.  for  each  100  gms.  phenyl- 
hydroxylamine) is  added  through  a  dropping  funnel.  The  addition  of 
amyl  nitrite  requires  about  30  minutes,  during  which  time  the  stream 
of  ammonia  is  continued,  so  that  ammonia  will  remain  in  excess  (other- 
wise a  coloured  product  results).  The  temperature  should  not  exceed 
10°  during  this  addition.  After  the  addition  of  the  nitrite  the  mixture 
is  stirred  for  10  minutes  to  ensure  complete  reaction.  The  cupferron 
is  then  filtered  off,  washed  several  times  with  ether,  and  dried  by  exposure 
on  sheets  of  filter  paper.  It  is  stored  in  a  bottle,  where  it  is  exposed  to 
the  vapours  of  ammonia  ;  this  is  effected  by  placing  a  small  tube  con- 
taining solid  ammonium  carbonate,  and  which  is  drawn  out  to  a  fine 
capillary,  inside  the  bottle  of  cupferron. 

/NO  yO 
C6H5NHOH  ->  C6H5N<;  or  C6H6NC 

\ONH4  ^NO.NH4. 

Yield.— 80— 90%  theoretical  (800  gms.). 

This  reagent  is  much  used  for  the  estimation  of  copper  and  iron  (hence 
its  name).    See  text-books  on  inorganic  analysis.    (Am.  Soc,  41,  276.) 
Peeparation  452. — Benzene  Sulphonyl  Chloride. 

C6H5S02C1.  176-5. 

150  gms.  of  sodium  benzene  sulphonate,  which  have  been  dried  for  3  hours 
at  140°,  are  mixed  with  85  gms.  of  finely  divided  phosphorus  pentachloride 
in  a  round-bottomed  flask  provided  with  a  reflux  condenser.  The  mixture 
is  heated  at  17 0° — 180°  in  an  oil  bath.  The  flask  should  be  removed  every 
4  hours,  stoppered,  and  vigorously  shaken  until  the  mass  becomes  pasty. 
The  mass  is  poured  into  a  mixture  of  ice  and  water,  when  the  benzene 
sulphonyl  chloride  sinks  to  the  bottom  ;  it  is  separated,  washed  with 
water,  and  distilled  in  vacuo,  the  fraction  145° — 150°  at  45  mms. 


MISCELLANEOUS  PREPARATIONS 


417 


being  collected.  The  phosphorus  pentachloride  may  be  replaced  by 
60  gms.  phosphorus  oxy chloride. 

3C6H5S02.ONa  +  PC15  =  3C6H6S02C1  +  2NaCl  +  NaP03. 
2C6H5S02.ONa  +  POCl3  =  2C6H5S02C1  +  NaCl  +  NaP03, 

Yield.— 75— 80%  theoretical  (110—120  gms.).  Colourless  oil;  M.P. 
14-5°  ;  B.P.760  2  46°  (decomposition).  (B.,  42,  1802,  2057  ;  "  Organic 
Syntheses,"  Vol.  I.,  Roger  Adams,  and  others.) 

Preparation  453.— a-Naphthalene  Sulphonyl  Chloride. 

S02C1. 


C10H7O2ClS  226-5. 


30  gms.  (1  mol.)  of  sodium  a-naphthalene  sulphonate  previously  dried 
at  150°  are  gradually  added  while  warm  to  30  gms.  (slight  excess)  of 
phosphorus  pentachloride  contained  in  a  basin  or  beaker.  The  reaction 
commences  on  the  addition  of  the  first  portions,  and  further  addition  is 
regulated  so  that  the  reaction  does  not  become  too  vigorous.  After  the  final 
addition  the  whole  is  heated  on  a  water  bath  until  homogeneous.  After- 
wards it  is  transferred  to  a  flask  and  distilled  under  reduced  pressure  until 
the  distillate — which  consists  at  first  of  phosphorus  oxy  chloride — weighs 
15 — 20  gms.  The  residue  in  the  flask  is  poured  into  a  mortar  and  stirred 
as  it  solidifies  ;  when  solid  it  is  mixed  with  ice  water,  ground  up  and 
filtered.  It  is  then  well  pressed  for  a  short  time  on  a  porous  plate,  and 
after  complete  drying  in  vacuo  over  sulphuric  acid,  is  recrystallised 
from  a  mixture  of  benzene  and  petroleum  ether. 

C10H7SO2OH  +  PC15  ->  C10H7SO2Cl  +  HC1  +  POCl3. 

Yield.— 60%  theoretical  (17-5  gms.).    M.P.  66°. 

f} -Naphthalene  sulphonyl  chloride  is  prepared  in  a  similar  manner  from 
sodium  ^-naphthalene  sulphonate.    (A.,  275,  233.) 
Preparation  454. — Ethyl  Potassium  Sulphate. 

C2H5O.S03K.       C2H504SK.  164. 

To  100  c.cs.  ethyl  alcohol  in  a  J-litre  round-bottomed  flask  are  carefully 
added  with  cooling  40  c.cs.  cone,  sulphuric  acid.  A  reflux  condenser  is 
attached  and  the  mixture  heated  for  an  hour  on  the  water  bath,  and  then 
allowed  to  cool.  The  liquid  is  poured  into  \  litre  of  water  in  a  porce- 
lain basin,  and  to  this  is  added  chalk,  with  stirring,  until  effervescence 
ceases..  The  calcium  sulphate  is  filtered  off,  and  washed  with  a  little 
warm  water.  To  the  filtrate,  which  contains  ethyl  calcium  sulphate, 
is  added  saturated  potassium  carbonate  solution  until  the  liquid  gives  a 
faint  alkaline  reaction  to  phenolphthalein.  The  calcium  carbonate  is 
filtered  off  and  washed  with  a  little  hot  water.  The  filtrate  is  then  evapo- 
rated until  crystallisation  begins,  when  it  is  set  aside  to  cool.    The  crystals 


s.o.c. 


E  E 


418  SYSTEMATIC  ORGANIC  CHEMISTEY 


of  ethyl  potassium  sulphate  are  filtered  off  and  dried,  and  a  further 
crop  obtained  hy  concentrating  the  mother  liquor. 

C2H5OH  +  H2S04  ->  C2H5O.S03H     >  (C2H5O.S03)2Ca  ->  C2H5O.S03K. 

Yield. — 15%  theoretical  (45  gms.).    Deliquescent,  monoclinic  plates  ; 
soluble  in  water  ;  insoluble  in  alcohol  or  ether.    (BL,  19,  295.) 
Preparation  455— Quinol  (1.4-Dihydroxybenzene). 

C6H4(OH)2.       C6H602.  110. 

10  gms.  of  finely  powdered  ^-benzoquinone  are  suspended  in  about 
100  c.cs.  of  water,  and  sulphur  dioxide  passed  in  until  the  odour  of  the  gas 
still  remains  after  standing  for  some  hours.  Should  the  odour  disappear 
saturation  is  repeated  until  the  solution  retains  the  smell  of  the  gas  on 
standing  overnight.  The  solution  is  then  extracted  a  few  times  with 
ether,  the  ether  distilled  off,  and  the  residue  recrystallised  from  a  little 
water  containing  sulphurous  acid  and  animal  charcoal. 

Yield. — Theoretical  (10  gms.).  Colourless  plates;  M.P.  169°;  soluble 
in  alcohol,  water  and  in  ether  ;  insoluble  in.  benzene ;  decomposes  when 
quickly  heated.     (B.,  19,  1467  ;  C,  1898  (2),  1007.) 

Preparation  456 . — Amino-azo-benzene. 

C6H5N  :  N.C6H4NH2.       C12HnN3.  197. 

10  gms.  of  finely  ground  diazoamino-benzene,  5  gms.  of  aniline  hydro- 
chloride, and  20  gms.  of  aniline  are  heated  in  a  beaker  at  40°  for  an  hour. 
After  standing  overnight  at  ordinary  temperature,  the  mixture  is  treated 
with  an  excess  of  dilute  acetic  acid  to  dissolve  the  aniline  ;  aminoazo- 
benzene  remains  undissolved.  It  is  filtered  off,  washed  with  water,  and 
recrystallised  from  dilute  alcohol. 

C6H5N  :  N.NH.C6H5  ->  C6H5N  :  N.C6H4NH2. 

Yellow  needles  ;  M.P.  126°  ;  stable  basic  substance.  (B.,  19,  1953  ; 
20,  372.) 

Preparation  457. — Nitrosobenzene, 

C6H5NO.  107. 

4-6  gms.  potassium  dichromate  (or  an  equivalent  quantity  of  sodium 
dichromate)  are  dissolved  in  200  c.cs.  water  and  the  solution  cooled  to  0° 
in  a  freezing  mixture.  A  mixture  containing  4  gms.  finely  powdered 
phenylhydroxylamine,  30  gms.  cone,  sulphuric  acid,  and  270  c.cs.  of  water 
is  also  cooled  in  ice  water,  and  to  it  the  dichromate  solution  is  added 
quickly.  The  nitrosobenzene  which  separates  is  removed  by  steam 
distillation,  and  if  any  solidifies  in  the  condenser,  the  water  should  be  run 
out  of  the  latter  until  the  solid  melts  and  flows  down  into  the  receiver. 
The  nitrosobenzene  is  filtered  off  from  the  distillate,  pressed  on  a  porous 
plate  until  dry,  and  washed  with  a  little  petroleum  ether. 

C6H5NH.OH  +  O  ->  C6H5NO  +  H20. 


M.P.  68°  ;  colourless  or  yellow  crystals.    (D.K.P.,  89978  ;  105875.) 


MISCELLANEOUS  PREPARATIONS 


419 


Preparation  458. — Aniline  Nitrate  (Phenyl-ammonium  nitrate). 
C6H5NH3.N03.       C6H803N2.  156. 
Aniline  Hydrochloride  (Phenyl-ammonium  chloride). 

C6H5NH8.C1.       C6H8NC1.  129-5. 

The  preparation  of  aniline  nitrate  is  fully  described  on  p.  368  under  the 
preparation  of  diazobenzene  nitrate.  The  crude  product  therein  obtained 
is  recrystallised  by  dissolving  in  a  little  absolute  alcohol  and  precipitating 
therefrom  with  ether.  The  preparation  and  purification  of  aniline 
hydrochloride  is  exactly  similar. 

C6H5NH2  +  HN03  =  C6H5NH3.N03. 
C6H5NH2  +  HC1  =  C6H5NH3.C1. 

Yields. — Aniline  Nitrate. — 80%  Theoretical  (13  gms.  from  10  gms.  of 
aniline).  Aniline  Hydrochloride. — 80%  Theoretical  (10  gms.  from  10 
gms.  of  aniline).  Colourless  crystals  ;  soluble  in  water  and  alcohol ; 
insoluble  in  ether  ;  aniline  hydrochloride  melts  at  192°  ;  aniline  nitrate 
transforms  to  nitraniline  at  190°.  (A.  Ch.,  [6],  21,  355  ;  J.,  1861,  495  ; 
B.,  14,  1083.) 

Aniline  Sulphate  (Di-phenyl-ammonium)  Sulphate. 

(C6H5NH3)2S04.       C12H1604N2S.  284. 

To  10  gms.  (2  mols.)  of  aniline  15  c.cs.  (an  excess)  of  dilute  (5N)  sulphuric 
acid  are  added.    The  precipitate  is  recrystallised  from  a  little  water. 

2C6H5NH2  +  H2S04  =  (C6H5NH3)2S04. 

Yield. — 90%  theoretical  (13 '5  gms.).  Colourless  crystals  ;  soluble  in 
water ;  slightly  soluble  in  absolute  alcohol ;  insoluble  in  ether.  (A. 
Ch.,  [6],  21,  355  ;  B.,  18,  3313.) 

Preparation  459. — Aniline  Hydroferrocyanide  (Phenyl  ammonium 
ferrocyanide). 

Aniline  is  dissolved  in  cone,  hydrochloric  acid  until  only  slightly  acid. 
Water  is  then  added  until  the  whole  is  a  saturated  solution  of  aniline 
hydrochloride  at  ordinary  temperature.  A  saturated  solution  of  sodium 
ferrocyanide  is  then  added  until  precipitation  is  complete.  The  solution 
should  be  slightly  acid  after  this  stage  has  been  reached.  The  white 
precipitate  is  filtered  off,  washed  first  with  a  little  alcohol  and  then  ether, 
and  dried  by  suction. 

2C6H5NH2  +  H4Fe(CN)6->  2C6H5NH2.H4Fe(CN)6[.2H2OJ. 

Yield. — Theoretical.  White  rhombohedral  crystals  with  greenish 
tinge  ;  infusible  ;  almost  insoluble  in  water,  solution  being  decomposed 
on  boiling  with  evolution  of  hydrocyanic  acid  ;  insoluble  in  alcohol  or 
in  ether.  Many  other  aromatic  organic  bases  yield  similar  compounds. 
(J.  C.  S.,  121,  1293.) 

E  E  2 


420  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  460.— ^-Benzoquinone  Dichlorimide. 


C1N<^      ^>NC1.       C6H4N2C12.  175. 

Chlorine  is  passed  into  250  c.cs.  water  containing  45  gms.  caustic  soda 
until  the  total  weight  is  332  gms.  750  c.cs.  of  ice-water  are  then  added, 
and  into  the  cold  solution  are  slowly  run  27  gms.  j9-phenylenediamine 
hydrochloride  in  300  c.cs.  of  water  and  60  c.cs.  of  cone,  hydrochloric  acid. 
After  the  blue  colour  disappears  the  dichlorimide  separates,  is  filtered  and 
washed  with  water  until  the  filtrate  is  free  from  chlorine ;  it  is  then 
recrystallised  from  70%  alcohol  or  petroleum  ether  (40° — 60°). 

NH2/       ^NH2  +  3C12  ->  C1N<^       ^>NC1  +  4HC1. 

Colourless  needles,  which  explode  at  126°  (caution  /).    (B.,  12,  47.) 
Preparation  461. — Alkyl  Nitrophenols  (l-Methoxy-2-nitrobenzene), 
etc. 

NQ2  NQ2 

CH30<^       \andCH30<^      ^>N02,        C2H50^      ^>  etc. 

o-Mtro-anisole.  o-Mtro-phenetole. 

70  gms.  of  ortho-  or  jpara-mtvo  phenol,  20  gms.  caustic  soda,  and  40 
gms.  sodium  carbonate  are  dissolved  in  200  c.cs.  water.  To  this  solution 
is  added  250  c.cs.  methyl  (or  ethyl)  alcohol,  90%,  and  the  whole  cooled 
to  10°  and  placed  in  an  autoclave.  1-75  gm.  mols.  methyl  (or  ethyl) 
chloride  (both  are  gases  at  ordinary  temperature)  are  then  added,  and 
the  temperature  is  raised  to  100°  for  8  hours — the  pressure  being  4—5 
atms.  The  product  is  poured  into  water  and  the  alkyl  ether  separated. 
The  alcohol  is  then  recovered.  The  alkyl  compound  is  washed  with  a 
little  caustic  soda  solution  to  remove  free  nitrophenol.  It  is  purified  by 
distillation. 

/       \OH   >    <^      ^>OCH3,  etc. 

Yield.— 75— 80%  theoretical  (55  gms.).  o-Nitroanisole  :  M.P.  9°  : 
B.P.  265°  ;  jo-nitroanisole  :  M.P.  54°  ;  B.P.  258°.  o-Nitrophenetole  : 
M.P.  78°  ;  B.P.  268°  ;  ^-nitrophenetole  :  M.P.  60°  ;  B.P.  283°.  (Z.  Ch., 
1913,  12,  171.) 

Preparation  462. — Potassium  Phthalimide. 

/co\ 

C6H4<       )NK.       C8H402NK.  185. 

2-4  gms.  phthalimide  (previously  dried  in  a  steam  oven)  are  dissolved 
in  80  c.cs.  ethyl  alcohol  (distilled  from  lime),  the  solution  is  heated  to 
boiling,  and  a  hot  solution  of  1  gm.  (1-|  atoms)  of  potassium  in  30  c.cs.  of 
ethyl  alcohol  added.  [The  potassium  ethoxide  is  prepared  by  dissolving 
the  potassium  in  alcohol  diluted  with  dry  ether,  which  is  afterwards 


MISCELLANEOUS  PEEP AR ATI ONS 


421 


driven  off  when  the  solution  is  raised  to  boiling  on  a  water  bath.]  When 
cold,  the  white  precipitate  is  filtered  off,  washed  with  dry  ether,  and  dried 
in  an  oven. 

7^.-68%  theoretical. 

Sodium  phthalimide  may  be  prepared  in  a  similar  manner,  the  yield 
being  50%  theoretical. 

Bv  using  amyl  alcohol  in  place  of  ethyl  alcohol  the  yields  may  be 
improved  to  above  90%  theoretical.    (J.  C.  S.,  121,  2362  ;  A.,  215,  181.) 

Preparation  463. — Phenyl-hydrazone  of  cZ-Mannose  (+  +  -f-  + 
Pentolhexanal). 

CH2(OH)(CH(OH))4CH :  NNH.C6H5.       C12H1805N2.  270. 

To  4  gms.  (1  mol.)  of  mannitol  dissolved  in  20  c.cs.  of  water,  and  a 
solution  of  1  gm.  of  ferrous  sulphate  in  cold  water  is  added,  and 
then  gradually,  12  c.cs.  (1  atom  of  0)  of  hydrogen  peroxide  solution 
(20  vols.),  or  more  if  solution  is  weaker,  are  dropped  in.  The  solution 
must  be  well  cooled  throughout.  Sodium  carbonate  solution  is  added  till 
just  alkaline,  the  whole  filtered,  and  a  portion  of  the  filtrate  tested  for 
mannose  by  Fehling's  solution,  and  by  ammoniacal  silver  nitrate.  To 
the  bulk  of  the  filtrate  1  c.c.  (excess)  of  phenylhydrazine  dissolved  in  a 
slight  excess  of  dilute  acetic  acid  is  added,  the  solution  allowed  to 
stand,  and  the  precipitate  of  mannose  phenylhydrazone  filtered  ofT.  It 
is  recrystallised  from  dilute  alcohol. 

CH2OH(CHOH)4CH2OH  +  O  -  CH2OH(CHOH)4CHO  +  H20. 

Yellow  crystals  ;  M.P.  198°. 
Preparation  464. — Diphenyl  Disulphide. 

C6H5S.SC6H5.       C12H10S2.  218. 

0-5  c.c.  (2  mols.)  of  thiophenol  are  dissolved  in  alcohol,  0-5  c.c.  of  cone, 
ammonia  added,  and  the  whole  evaporated  to  dryness  on  a  water  bath 
in  a  good  fume  cupboard. 

2CfiH5SH  +  O  =  C6H5S.SC6H5  +  H20. 

Yield. — Theoretical.    Colourless  needles  ;  M.P.  61°. 
Preparation  465. — lodoso-benzene  ( ( Oxy-iod) -benzene). 

C6H5.I  :  O.       C6H5OI.  220. 

By-product. — Diphenyl  lodonium  Iodide  (Phenyliodide  derivative  of 
iod-benzene). 

(C6H5)2 :  LI.       C12H10I2.  408. 

10  gms.  (1  mol.)  of  phenyliodide  dichloride  are  carefully  rubbed  with 
a  solution  of  5  gms.  of  sodium  hydroxide  in  40  gms.  of  water  in  a  mortar 
and  allowed  to  stand  overnight.  The  iodosobenzene  is  filtered  off, 
washed  with  water,  and  pressed  on  a  porous  plate.    The  alkaline  filtrate 


422  SYSTEMATIC  ORGANIC  CHEMISTRY 


is  saturated  with  sulphur  dioxide,  and  the  precipitated  diphenyl  iodonium 
iodide  crystallised  from  a  small  quantity  of  hot  water,  or  from  alcohol. 

C6H5I  :  CL  +  2H20  =  C6H5I(OH)2  +  2HC1 

=  C6H5.I  :  0  +  H20  +  2HC1. 

A  small  portion  of  the  iodosobenzene  is  probably  oxidised  to  iodoxy- 
benzene,  C6H5I02,  which  reacts  with  the  hypothetical  hydroxide, 
CGH5.I(OH)2,  to  give  diphenyl  iodonium  hydroxide  and  iodic  acid.  This 
base  is  present  in  the  alkaline  filtrate  from  the  iodosobenzene.  The 
sulphur  dioxide  reduces  the  iodic  acid  to  hydriodic  acid,  which,  combining 
with  the  iodonium  base,  forms  an  iodide  insoluble  in  cold  water. 

C6II5-I.;OH      I02jC6H5  =  C6H5.I(OH).C6H5  +  HI03. 
OH  + 

HI03  +  3S02  +  3H20  =  HI  +  3H2S04. 
(C6H5)2I.OH  +  HI  =  (C6H5)2I.I  +  H20. 

Yields. — Iodosobenzene. — 75%  theoretical  (9  gms.).  White  amorphous 
substance  ;  soluble  in  water,  yielding  a  neutral  solution  ;  decomposes 
when  heated  to  above  240°. 

Diphenyl  Iodonium  Iodide. — Crystallises  from  alcohol  in  long,  yellow 
needles  ;  M.P.  175° — 176°  ;  on  melting  decomposes  completely  into 
iodobenzene.    (B.,  25,  3495  ;  26,  1307,  1354  ;  27,  506.) 

Preparation  466. — lodoso-lbenzene  Acetate  (Di-acetyl  derivative 
of  phenyl-di-hydroxy  iodine). 

C6H5I  :  (O.CO.CH3)2.       C10HnO4I.  322. 

5  gms.  (1  mol.)  of  iodosobenzene  are  dissolved  with  heat  in  the  smallest 
possible  quantity  of  glacial  acetic  acid,  the  solution  evaporated  to  dryness 
on  a  water  bath,  and  the  powdered  residue  recrystallised  from  a  little 
benzene. 

C6H5I  :  0  +  2CH3COOH  =  C6H5I  :  (O.CO.CH3)2  +  H20. 

Yield.— Theoretical  (7  gms.).    Colourless  prisms  ;  M.P.  156°— 157°. 
Preparation  467. — Iodoxy-benzene  (Phenyl  iodite). 

C6H5.I02.       C6H502L  236. 

10  gms.  (1  mol.)  of  iodosobenzene  are  mixed  in  a  flask  with  sufficient 
water  to  form  a  thin  paste,  and  steam-distilled  until  no  more  iodobenzene 
comes  over,  and  until  all  the  iodosobenzene  has  completely  reacted.  If 
the  iodoxybenzene  formed  does  not  dissolve  completely,  water  is  added 
until  solution  takes  place.  The  residue  is  then  filtered  and  concentrated 
on  a  water  bath  until  a  test  portion,  on  cooling,  gives  a  copious  precipitate. 

2C6H5I  :  0  =  C6H5I.02  +  C6H5I. 

Snow-white  powder  ;  decomposes  suddenly  on  heating  to  210° — 230°. 
Preparation  468. — Diphenyl  Iodonium  Iodide  (Phenyl-iodide  of  iod- 
benzene). 

(C6H5)2I.I.       C12H10I2.  408. 
10  gms.  (1  mol.)  of  iodosobenzene  and  11  gms.  (1  mol.)  of  iodoxybenzene 


MISCELLANEOUS  PREPARATIONS 


423 


are,  treated  with  water  and  with  20  gms.  (excess)  of  freshly  precipitated 
silver  oxide  in  a  stout,  well-stoppered  bottle,  shaken  mechanically  for 
4  hours,  and  filtered.  The  filtrate,  which  contains  free  diphenyliodonium 
hydroxide,  has  a  strongly  alkaline  reaction.*  The  base  has  not  been 
obtained  in  a  pure  form,  but  its  salts  are  readily  prepared  from  the 
solution. 

The  solution  contains  part  of  the  base  in  the  form  of  its  iodate,  and  is 
therefore  first  treated  with  sulphur  dioxide,  and  then  with  excess  of 
potassium  iodide  solution,  when  the  iodide  separates  out  completely. 
It  is  recrystallised  from  alcohol. 

C6H51 :  0  +  C6H5I02  +  AgOH  ->  (C6H5)2I.OH  +  AgI03. 
(C6H5)2I,OH  +  KI  ->  (C6H5)2I.I. 

Yield. — 93%  theoretical  (17  gms.).  Yellow  needles  from  alcohol ; 
M.P.  175° — 176°  ;  on  melting  decomposes  completely  into  iodobenzene. 
(B.,  27,  426  ;  502,  1592.) 

Preparation  469— Phenyl-iodide  Dichloride. 

C6H5.I  :  Cl2.       C6H5C12I.  275. 

10  gms.  (1  mol.)  of  iodobenzene  are  dissolved  in  20  c.cs.  of  dry  chloro- 
form, and  a  current  of  chlorine,  dried  by  bubbling  through  two  concentrated 
sulphuric  acid  wash  bottles,  is  led  into  the  solution  through  a  very  wide 
delivery  tube.  During  the  passage  of  the  gas  the  solution  is  cooled  by 
ice  water  ;  when  no  more  gas  is  absorbed  the  yellow  crystals  are  filtered 
off,  washed  with  chloroform,  spread  out  in  a  thin  layer  on  a  pad  of  filter 
paper,  and  allowed  to  dry  in  the  air. 

C6H5I  +  Cl2  =  C6H5I :  Cl2. 

Yield. — Almost  theoretical  (13  gms.).    Very  unstable  yellow  crystals  ; 
decompose  on  heating.    (J,  pr.,  33,  154  ;  B.,  26,  357  ;  A.,  369,  119.) 
Preparation  470. — ^-Naphthalene  Sulpho-glycine. 

C10H7.SO2.NH.CH2.COOH.       C12Hn04NS.  265. 

2  gms.  (1  mol.)  of  glycocoll  are  dissolved  in  27  c.cs.  (1  mol.)  of  normal 
sodium  hydroxide,  and  to  this  an  ethereal  solution  of  12  gms.  (2  mols.)  of 
/3-naphthalene-sulphonyl  chloride  is  added.  The  mixture  is  shaken  in  a 
stoppered  bottle  in  a  shaking  machine  at  ordinary  temperature.  Three 
times,  at  intervals  of  about  an  hour,  the  same  amount  of  normal  alkali  is 
again  added.  After  about  4  hours  the  aqueous  liquid,  which  still  reacts 
alkaline,  is  separated  from  the  ethereal  layer  in  a  funnel,  filtered,  and 
acidified  with  hydrochloric  acid.  The  oil  which  is  precipitated  soon 
crystallises.    For  complete  purification  it  is  recrystallised  from  hot  water 

C10H7.SO2Cl  +  NH2.CH2.COOH  =  C10H7SO2.NHCH2.COOH  +  HC1. 

Colourless  laminse,  M.P.  156°  (159°  corr.).    (B.,  35,  3780.) 

*  Test  solution  for  an  iodate. 


424  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  471. — Thiophenol. 

C6H5SH.       C6H6S.  110. 

This  experiment  should  be  performed  in  a  good  draught  chamber. 
240  gms.  cone,  sulphuric  acid  and  720  gms.  crushed  ice  are  placed  in 
a  litre  round-bottomed  flask.  The  mixture  is  cooled  by  placing  the 
flask  in  a  freezing  mixture  ;  the  temperature  should  be  kept  below  0°. 
Stirring  is  commenced,  and  60  gms.  benzene  sulphonyl  chloride  (see 
p.  416)  are  gradually  run  in  during  \  hour.  120  gms.  of  zinc-dust  are 
then  added  as  quickly  as  possible  without  allowing  the  temperature  to 
rise  above  0° ;  this  requires  about  \  hour.  The  stirring  is  continued  for 
1 — \\  hours,  the  temperature  being  kept  below  0°.  A  reflux  condenser 
is  now  attached,  the  freezing  bath  is  removed,  and  the  temperature  allowed 
to  rise  spontaneously  or  by  the  application  of  a  little  heat,  the  agitation 
being  maintained.  A  vigorous  action  ensues  after  a  time,  and  much 
hydrogen  is  evolved,  at  which  stage  cooling  should  be  applied.  The 
mixture  is  then  heated  to  boiling  until  the  solution  becomes  clear  (about 
4 — 7  hours).  The  thiophenol  is  steam-distilled,  separated  from  the 
water,  and  dried  with  calcium  chloride.  It  is  distilled,  the  fraction 
boiling  at  166°— 175°  (71°  at  15  mms.)  is  collected. 

C6H5S02CI  +  6H  ->  C6H5SH  +  2H20  +  HC1. 

Yield.— 90%  theoretical  (34  gms.).  Colourless  liquid ;  B.P.  173°  ; 
characteristic  unpleasant  odour  ;  produces  burns  on  the  skin  :  vapour 
irritates  the  eyes.    (A.,  119,  142  ;  B.,  28,  2319  ;  51,  751.) 

Peeparation  472. — Lead  and  Mercury  Salts  of  Thiophenol. 

(C6H5S)2Pb.  (C6H5S)2Hg. 
C12H10S2Pb.       425.       C12H10S2Hg.  418. 

1  gm.  (excess)  of  lead  acetate  or  mercuric  chloride  is  dissolved  in  alcohol 
by  the  application  of  heat,  and  the  solution  cooled  and  filtered.  0-5  c.c. 
(2  mols.)  of  thiophenol  are  then  added  drop  by  drop  when  a  precipitate  of 
the  required  salt  is  obtained.    It  is  washed  with  a  little  alcohol. 

2C6H5SH  +  (CH3COO)2Pb  =  (C6H5S)2Pb  +  2CH3.COOH. 
2C6H5SH  +  HgCl2  =  (C6H5S)2Pb  +  2HC1. 

Yield. — Theoretical  (1  gm.).  Crystalline  substances  ;  insoluble  in 
alcohol. 

Preparation  473. — Lead  and  Calcium  Salts  of  Glyceric  Acid. 

(Pb  or  Ca)[O.CO.CH(OH)CH2OH]2. 

Pb  Salt. — A  dilute  aqueous  solution  of  glyceric  acid  (p.  242)  is  neutralised 
with  lead  carbonate  containing  a  small  quantity  of  lead  oxide.  The  mix- 
ture is  heated  to  boiling  and  filtered  hot.  The  filtrate,  on  concentrating 
and  cooling,  yields  the  required  salt  in  crusts,  which  adhere  to  the  sides 
of  the  vessel.  A  further  crop  may  be  obtained  by  concentrating  and 
cooling  the  mother  liquors.  The  product  may  be  recrystallised  from  hot 
water. 


MISCELLANEOUS  PREPARATIONS 


425 


Yield. — -Theoretical  (twice  the  weight  of  acid  taken). 

Ca  Salt. — A  dilute  aqueous  solution  of  glyceric  acid  is  boiled  with  excess 
of  calcium  carbonate  and  filtered  hot.  The  nitrate,  on  concentrating 
and  cooling,  yields  colourless  crystals  of  the  required  salt,  which  may  be 
recrystallised  from  hot  water.    (A.,  120,  226.) 

Peepaeation  474.  —  Triphenyl  -  chloromethane  (Triphenylmethyl 
chloride). 

(C6H5)3CC1.       C19H15C1.  278-5. 

12-5  gms.  of  freshly  prepared,  finely  divided  anhydrous  aluminium 
chloride  (see  p.  503)  are  added  in  4  equal  portions  to  a  mixture  of  10  gms. 
(1  mol.)  of  redistilled  carbon  tetrachloride,  which  has  stood  for  48  hours 
over  calcium  chloride,  and  35  gms.  (excess)  of  pure  similarly  treated 
benzene,  in  a  flask  fitted  with  a  long  reflux  condenser.  When  the  reaction 
moderates,  it  is  completed  by  heating  on  a  water  bath  for  1  hour.  On 
cooling,  the  contents  of  the  flask  are  very  slowly  poured  with  mechanical 
stirring  on  to  ice  surrounded  by  a  freezing  mixture.  Three  times  during 
the  addition  benzene  is  added,  sufficient  to  dissolve  the  triphenyl-chloro- 
me thane  as  it  separates.  The  benzene  solution  is  separated,  washed  with 
dilute  hydrochloric  acid,  then  with  water,  dried  over  calcium  chloride,  and 
evaporated  on  a  water  bath  until  triphenyl-chloromethane  crystallises, 
on  cooling  a  sample.  After  filtration,  a  further  yield  may  be  obtained 
by  removing  the  benzene  under  reduced  pressure  at  40°,  and  washing 
the  residue  with  ether.  The  whole  is  purified  by  retreatment  with 
benzene,  as  above. 

3C6H6  +  CC14  ->  C1C(C6H5)3  +  3HC1. 

Yield. — 80%  theoretical  (14  gms.).    Colourless  crystals  ;  somewhat 
soluble  in  benzene  ;  M.P.  108°— 112°.    (A.,  194,  253.) 
Prepaeation  475— Thianthren  (Di-thio-di-phenylene), 

C6H4<^>C6H4.       C12H8S2.  216. 

To  the  catalyst  prepared  as  described  on  p.  57,  from  25  gms.  of 
aluminium  powder,  45  gms.  of  mercuric  chloride  and  25  gms.  (excess) 
of  pure  dry  benzene,  10  gms.  (4  atoms)  of  flowers  of  sulphur  are  added 
under  good  mechanical  stirring,  and  the  mixture  heated  on  a  water  bath 
until  hydrogen  sulphide  is  no  longer  evolved.  The  product,  on  cooling, 
is  decomposed  by  adding  ice,  filtered,  and  the  residue  repeatedly  extracted 
with  chloroform,  from  which  the  thianthren  is  obtained  on  concentration. 
It  is  recrystallised  from  acetone. 

AlCl3HgCl  .Sv 
2C6H6  +  2S  >    C6H4/  g/>C6H4. 

Yield. — 80%  theoretical  (14  gms.).    Colourless  crystals  ;    soluble  in 
chloroform  ;  insoluble  in  cold  acetone  ;  M.P.  160°.    (J.  C.  S.,  117,  1335.) 
This  is  an  extension  of  the  Friedel-Craft's  Reaction  (see  p.  56). 


426  SYSTEMATIC  ORGANIC  CHEMISTRY 


The  Hydration  of  Unsaturated  Hydrocarbons  to  Yield  Oxy-compounds. 

The  recent  developments  in  the  production  of  acetaldehyde  from 
acetylene  have  given  a  new  stimulus  to  this  type  of  reaction  ;  hitherto 
such  examples  of  hydration  were  of  comparatively  little  importance. 

In  the  presence  of  moderately  dilute  sulphuric  acid  isobutylene  is  con- 
verted into  trimethyl  carbinol,  a  reaction  which  represents  one  step  in  the 
purification  of  hydrocarbon  oils. 

(CH3)2C  :  CH2  +  H20  ->  (CH3)3C.OH. 

For  the  preparation  of  acetaldehyde,  acetylene  is  led  into  20 — 45% 
sulphuric  acid,  or  30 — 35%  phosphoric  acid  or  96%  acetic  acid,  or  a 
strong  organic  sulphonic  acid,  all  in  presence  of  a  mercury  salt.  The 
action  probably  consists  (1)  in  the  formation  of  a  double  compound 
between  acetylene  and  the  mercury  salt,  and  (2)  the  decomposition  of 
this  compound  with  formation  of  acetaldehyde.  In  addition  to  acetalde- 
hyde there  is  likely  to  be  formed  some  of  its  condensation  products  and 
polymerides. 

For  further  consideration  of  such  reactions,  the  monographs  on  catalysis 
by  Henderson,  and  by  Rideal  and  Taylor,  should  be  consulted. 
Preparation  476. — Acetaldehyde. 

CHg.CHO.       C2H40.  44. 

Acetylene  prepared  from  calcium  carbide  and  purified  by  passing 
(1)  through  copper  sulphate  solution,  and  (2)  through  a  tower  packed 


Fig.  54. 

with  bleaching  powder,  is  led  into  a  flask  containing  300  c.cs.  of  96% 
acetic  acid  and  9-5  gms.  mercuric  sulphate  in  solution,  the  temperature 
of  which  is  kept  at  30°  (see  Fig.  54).  The  exit  tube  from  the  flask  is 
connected  (1)  to  a  cold  water  condenser,  and  (2)  to  two  wash-bottles 
containing  ether,  and  cooled  in  ice.  The  gas  should  be  passed  at  a  very 
moderate  rate  for  1  or  2  days,  and  a  little  water  (1 — 2  c.cs.)  added  at 


MISCELLANEOUS  PKEPARATIONS 


427 


intervals  to  replace  that  taken  up  in  the  reaction.  When  it  is  decided 
to  discontinue  the  reaction  the  flask  is  warmed  to  60° — 70°  to  drive  all 
the  aldehyde  over  into  the  ether.  The  ethereal  solution  is  dried  over 
anhydrous  sodium  sulphate,  then  decanted,  and  saturated  with  dry 
ammonia".    A  very  good  yield  of  aldehyde-ammonia  results. 

CH  ;  CH  4  H20  ->  CH3.CHO. 
CH3.CHO  +  NH3  ->  CH3CHOH.NH2. 

The  experiment  shows,  with  the  use  of  simple  apparatus,  the  preparation 
of  acetaldehyde  from  acetylene.  With  more  elaborate  apparatus  involving 
thorough  agitation  of  the  gas  with  the  catalyst,  and  also  a  circulatory 
system  by  which  the  escaping  acetylene  can  be  repeatedly  passed  through, 
the  catalyst,  excellent  yields  can  be  obtained. 

Preparation  477. — Paracetaldehyde. 

(CH3CHO)3.       C6H1203.  132. 

A  paste,  consisting  of  10  gms.  mercuric  sulphate,  and  40  gms.  of  ammo- 
nium hydrogen  sulphate  with  20  c.cs.  of  water  is  introduced  into  a  strong 
glass  bottle  of  1,500  c.cs.  capacity.  The  bottle  is  three  parts  filled  with 
glass  beads  and  thoroughly  shaken  ;  it  is  then  fitted  with  a  one-holed 
cork  carrying  a  delivery  tube,  which  passes  down  through  the  beads. 

j  A  current  of  acetylene,  prepared  from  calcium  carbide  and  water,  and 
purified  by  passing  first  through  copper  sulphate  solution,  and  then 
through  a  tower  packed  with  bleaching  powder,  is  led  into  the  bottle, 
which  has  no  outlet  and  which  is  periodically  shaken. 

In  about  2  hours  the  beads  adhere  together  somewhat ;  then  para- 
cetaldehyde begins  to  collect  at  the  bottom  of  the  bottle.    Water  is 

i  added,  2 — 3  c.cs.  at  a  time,  at  intervals  during  the  formation.    The  yield 

i  is  good,  and  there  is  practically  no  escape  of  acetylene  or  acetaldehyde 
from  the  apparatus.  The  action  consists  in  the  formation  of  a  mercuric 
sulphate  acetylene  compound  and  its  subsequent  decomposition  giving 
paracetaldehyde.  The  passage  of  acetylene  should  be  continued  for  about 
2  days.    The  contents  of  the  bottle  are  finally  shaken  up  with  ether,  the 

j  ethereal  solution  separated,  dried  over  anhydrous  sodium  sulphate, 
and  distilled.  Paracetaldehyde  passes  over  as  a  colourless  liquid,  boiling 
point  124°. 

3C2H2  +  3H20  ->  (CH3CHO)3. 
(Am.  Soc,  43,  2071.) 

Preparation  478. — Chloroform  (Trichlormethan). 

CHC13.  119-5. 

100  gms.  of  fresh  35%  bleaching  powder,  or  an  equivalent  quantity,  are 
j  ground  up  in  a  mortar  to  a  paste  with  water  and  washed  with  water  into 
a  2-litre  flask,  400  c.cs.  of  water  being  used  altogether.  (Note. — As  com- 
mercial bleaching  powder  is  rather  variable,  the  sample  should  be  analysed, 
and  the  correct  equivalent  quantity  taken,  otherwise  poor  yields  are 
obtained.)    20  gms,  rectified  spirit  (or  acetone)  are  placed  in  the  flask. 


428 


SYSTEMATIC  ORGANIC  CHEMISTRY 


which  is  connected  to  a  long  condenser  and  receiver.  The  flask  is  gently 
warmed  on  a  sand  bath  until  a  reaction  commences,  when  the  flame  is 
withdrawn  until  the  reaction  subsides  ;  much  frothing  takes  place  at  this 
stage  if  the  reaction  is  going  properly.  Heat  is  again  applied  and  dis- 
tillation continued  so  long  as  any  oily  drops  of  chloroform  pass  over.  The 
distillate  is  placed  in  a  separating  funnel,  and  the  bottom  layer  of  chloro- 
form run  off.  This  is  washed  with  dilute  sodium  hydroxide,  dried  over 
granular  calcium  chloride  and  distilled. 

Yield. — (20  gms.).  Colourless  liquid  ;  B.P.  61°  ;  when  made  from 
alcohol  it  contains  a  little  ethyl  chloride. 

The  ultimate  changes  are  represented  by  the  following  equations  : — 

4C2H5OH  +  8Ca(OCl)2  — >  2CHC13  +  3Ca(COOH)2  +  5CaCl2  +  8H20. 
CH3.CO.CH3  +  3C12  ->  CH3COC.CI3  +  3HC1. 
2CH3.CO.CCl3  +  Ca(OH)2  ->  (CH8COO)aCa  +  2CHC13. 

(A.,  23,  244  ;  J.  Eng.,  1912,  IV.,  345  and  406.) 
Preparation  479.— Iodoform. 

CHI3.  394. 

From  Alcohol. — 32  gms.  potassium  carbonate  are  dissolved  in  80  gms. 
water  and  16  gms.  95%  alcohol,  and  the  solution  heated  to  70°.  32  gms. 
powdered  iodine  are  then  added  gradually  with  stirring.  Iodoform  gradu- 
ally separates  out,  and  when  the  solution  has  become  completely  decolor- 
ised, is  filtered  off,  washed  with  water,  and  dried  at  ordinary  tempera- 
ture. A  further  yield  is  obtained  by  adding  2 — 3  gms.  potassium  bichro- 
mate and  16 — 24  gms.  cone,  hydrochloric  acid,  neutralising  and  adding 
32  gms.  potassium  carbonate,  16  gms.  95%  alcohol  and  6  gms.  iodine,  and 
carrying  out  as  before. 

The  iodoform  is  then  recrystallised  from  alcohol. 

C2H5OH  +  4I2  +  6KOH  ->  CHI3  +  HCOOK  +  5KI  +  5H20. 

Lemon  yellow  hexagonal  crystals  ;  M.P.  115°  ;  characteristic  odour 
and  taste  ;  sparingly  soluble  in  water.    (J.,  1894,  317.) 

From  Acetone. — 100  gms.  iodine  are  dissolved  in  320  gms.  warm  10% 
caustic  soda  solution,  and  after  cooling,  20  gms.  of  acetone  added. 
100  gms.  powdered  iodine  are  added  with  stirring  and  then  caustic  soda 
solution  gradually,  until  the  iodine  disappears.  The  iodoform  separates 
and  is  filtered  off.  20  gms.  acetone  are  added  to  the  filtrate,  which  has 
been  acidified  with  hydrochloric  acid,  and  then  made  alkaline  with  caustic 
soda  and  a  further  yield  of  iodoform  obtained. 

Yield.— (180  gms.).    (A.  Spl.,  7,  218,  377.) 

Preparation  480. — Thiourea  (Thiocarbamide). 

NH2 

S :  C<  CH4N2S.  76. 

XNH2. 

50  gms.  of  ammonium  thiocyanate  are  melted  in  a  round-bottomed 
flask  in  a  paraffin  bath  and  kept  at  a  temperature  at  which  the  mass 


STEOCJS  '  PREPARATIONS  429 

remains  just  liqu,  M0° — 150°)  for  5— G  hours,  or  at  170°  for  1  hour. 
The  former  metho>  /es  the  better  yield.  The  cooled  melt  is  powdered 
and  ground  up  with  i  alf  its  weight  of  cold  water,  which  dissolves  unchanged 
ammonium  thiocyaLite,  but  little  of  the  thiourea.  The  residue  is  re- 
crystallised  from  hot  water. 

CNS.(NH4)  ^  CS(NH2)2. 

Yield. — 14 — 16%  of  complete  conversion  (7 — 8  gms.)  ;  slightly  soluble 
in  cold  water  (1  in  11)  ;  soluble  in  hot  water  and  alcohol ;  almost 
insoluble  in  ether  or  benzene  ;  M.P.  172°.  (J.  C.  S.,  22,  1  ;  83,  1  ; 
J.  pr.  [2],  9,  10.) 

Preparation  481. — Urea  (Carbamide). 

CO<  CH4ON2.  60. 

XNH2. 

Volhard's  Method. — 39  gms.  potassium  cyanide  and  10  gms.  caustic 
potash  are  dissolved  in  100  c.cs.  of  water  in  a  large  flask.  63  gms.  potassium 
permanganate  dissolved  in  1  litre  of  water  are  then  added,  drop  by  drop, 
from  a  funnel,  the  flask  being  placed  in  a  freezing  mixture.  The  tem- 
perature should  not  rise  above  8°.  This  is  filtered,  and  a  solution  of 
80  gms.  ammonium  sulphate  is  added,  and  the  whole  evaporated  to  dry- 
ness. The  residue  is  powdered  and  extracted  with  80  c.cs.  absolute 
alcohol  under  a  reflux  at  boiling  point  for  |  hour.  It  is  then  filtered  and 
the  residue  washed  with  boiling  alcohol.  The  alcohol  is  removed  by 
distillation  until  the  volume  is  about  50  c.cs.  It  is  then  placed  in  a 
glass  dish  and  allowed  to  stand.  The  crystals  which  separate  are  filtered, 
washed  with  alcohol,  and  dried.  A  second  crop  of  crystals  can  be  obtained 
from  the  mother  liquor. 

Prisms  ;  M.P.  132°  ;  verv  soluble  in  water  ;  insoluble  in  chloroform. 
(J.,  1880,  393.) 

Preparation  482. — Methylamine  Hydrochloride. 

CH3.NH2.HCl.       CH6NC1.  67-5. 

125  gms.  ammonium  chloride  and  250  gms.  40%  aqueous  formaldehyde 
solution  are  placed  in  a  distilling  flask  with  thermometer  well  below 
surface  of  liquor.  The  flask  is  attached  to  a  water  condenser,  and 
slowly  heated  until  the  thermometer  registers  104°,  at  which  it  is  main- 
tained constant  until  no  further  liquid  distils  over.  Weight  of  distillate  — - 
54  gms.  The  product  in  the  flask  is  cooled  and  filtered  from  ammonium 
chloride  which  separates.  The  filtrate  is  evaporated  on  a  water  bath  to 
half  its  original  volume,  cooled  and  a  second  crop  of  ammonium  chloride 
filtered  off.  The  liquid  is  then  concentrated  at  100°  until  a  crystalline 
scum  forms  on  the  surface.  On  cooling,  methylamine  hydrochloride 
separates,  and  is  filtered  off.  After  further  evaporation  and  cooling,  a 
second  crop  of  methylamine  hydrochloride  is  similarly  obtained.  The 
filtrate  is  again  concentrated,  and  left  for  24  hours  over  solid  caustic  soda 
in  a  vacuum  desiccator  ;  the  semi-solid  residue  is  extracted  with  warm 


430  SYSTEMATIC  OKGAMO  ^  ~ 

chloroform  which  dissolves  out  ai,                  ulu'  irochloride,  and  a 

further  quantity  of  methylamine  hvdr^Moride  is  .red  off.    The  total 

yield  is  treated  with  boiling  chloroform  ,  washed  with  warm 
chloroform,  and  dried  in  a  desiccator. 

/OH 

H.CHO  +  NHg.HCl  ->  H.CH<  ->  H.CH  :  NH.HC1  +  H20. 

\NH2.HC1 

CH2:  NII.HC1  +  H20  +  H.CHO  ->  CH3.NH2. HC1  +  H20. 

Yield. — 85%  theoretical  (50  gms.).    Large  deliquescent  plates  ;  in- 
soluble in  chloroform.    (J.  C.  S.,  Ill,  844.) 
Pkepakation  483. — /i/)-Dinaphthylamine. 

(C10H7)2NH.       C20H15N.  269. 

100  gms.  of  ^-naphthylamine  and  0-5  gms.  of  iodine  are  heated  to  230° 
for  4  hours.    The  melt  is  then  cooled  and  recrystallised  from  benzene. 

2C10H7NH2  ->  (C10H7)2NH  +  NH3. 

Yield. — Almost  theoretical  (185  gms).  Silver  glistening  plates  ;  M.P. 
170-5°  ;  sparingly  soluble  in  hot  alcohol ;  easily  soluble  in  hot  glacial 
acetic  acid.    (C,  1900,  II.,  1093.) 

Preparation  484. — Phenyl-/? -naphthylamine. 

C10H7NH.C6H5.       C16H13N.  219. 

90  gms.  of  /?-naphthol  and  112-5  gms.  of  aniline  are  heated  for  7  hours 
to  100° — 190°  with  1  gm.  of  iodine.  The  melt  is  boiled  out  first  with  dilute 
hydrochloric  acid  and  then  with  dilute  caustic  soda.  The  residue  is  dried 
and  distilled  in  vacuo.  The  phenylnaphthylamine  passes  over  at  237° 
(15  mms.).    It  is  recrystallised  from  methyl  alcohol. 

C10H7OH  +  H2N.C6H5  ->  C10H7NH.C6H5  +  H20. 

Yield.— Almost  theoretical.    Needles  ;  M.P.  108°.    (B.,  13,  1850.) 
Peeparation  485. — Thiocarbanilide. 

CS(NHC6H5)2.       C13H12N2S.  228. 

50  gms.  carbon  disulphide  and  40  gms.  aniline  are  dissolved  in  60  c.cs. 
alcohol  and  10  gms.  powdered  caustic  potash  are  added.  The  whole  is 
heated  (caution  /)  on  a  boiling  water  bath  for  3 — 4  hours  under  a  long 
reflux  condenser.  (Carbon  disulphide  boils  at  46°.)  The  carbon  disulphide 
and  alcohol  are  then  distilled  off  and  the  residue  is  washed  with  water  and 
with  dilute  hydrochloric  acid  to  remove  unchanged  aniline.  It  is  then 
filtered,  washed  with  water,  and  recrystallised  from  alcohol. 

Yield.— 70%  theoretical  (35  gms.).  Colourless  plates;  M.P.  151°; 
sparingly  soluble  in  water.   (A.  70,  142  ;  B.,  33,  2726.) 

Preparation  486. — Phenylglycine. 

C6H5NH.CH2COOH.       C8H902N.  139. 
20  gms.  of  chloracetic  acid  are  dissolved  in  20  c.cs.  of  water,  and  16  gms. 


MHCELLANEOUS  PREPAEATIONS 


431 


of  calcium  hydroxide  added,  the  whole  being  kept  cool :  a  mixture  of  20  c.c. 
of  methyl  or  ethyl  alcohol  and  60  gms.  of  aniline  is  next  added,  and  the 
whole  stirred  and  warmed  until  the  reaction  is  complete.  The  alcohol  and 
aniline  are  distilled  off  with  steam  ;  the  calcium  salt  is  filtered  off  and  is 
converted  into  the  sodium  salt  when  cold  (see  p.  303).  The  calculated 
amount  of  a  mineral  acid  is  added  to  the  concentrated  solution  of  the 
sodium  salt  and  the  phenyl  glycine  thus  obtained. 

^>NH2  +  C1CH2.C00H  — >    <^      ^NH.CH2.COOH  +  HOI. 

Small  crystals.    M.P.  126°— 127°.    (D.R.P.,  167698.) 
Preparation  487. — Phenylglycine-o-carboxylic  Acid. 

/COOH 

C6H4<  C9H904N.  195. 

\NH.CH2COOH. 

11-2  gms.  of  caustic  potash  are  dissolved  in  100  c.cs.  water,  and  to 
this  is  added  9-4  gms.  chloracetic  acid  and  13-6  gms.  anthranilic  acid. 
The  solution  is  warmed  on  a  water  bath  under  a  reflux  for  2  hours  at  60° — 
80°.  Hydrochloric  acid  is  then  added  to  neutralise  and  after  standing 
the  phenylglycine-o-carboxylic  acid  separates  out  and  is  filtered  off  and 
recrystallised  from  water.  A  further  yield  can  be  obtained  by  evaporating 
the  filtrate. 

/COOH  /COOH 
C6H4<  +  C1CH2C00H    ->  C6H4< 

\NH2  \NH.CH2COOH. 

Colourless  crystals.  M.P.  200°  (with  decomposition).  Sparingly 
soluble  in  water.  Solution  in  alcohol  shows  a  blue  fluorescence.  (B.,  23, 
3432.) 

Preparation  488. — Glycine  (Glycocoll). 

CH2NH2COOH.       C2H502N.  75. 

104  gms.  of  chloracetic  acid  are  dissolved  in  an  equal  weight  of  water, 
and  this  solution  slowly  run  into  1,248  c.cs.  of  25%  ammonia,  the  whole 
being  stirred  well.  When  all  the  acid  has  been  added  the  solution  is  set 
aside  for  24  hours  and  then  boiled  until  no  more  ammonia  is  evolved.  It 
is  made  neutral  while  hot  with  a  slight  excess  of  copper  carbonate,  filtered, 
and  the  filtrate  evaporated  until  it  begins  to  crystallise.  On  allowing 
to  cool  the  copper  salt  of  glycocoll  separates  as  blue  needles,  is  filtered 
and  washed  first  with  dilute,  and  then  with  more  concentrated  alcohol. 
The  salt  is  dissolved  in  water,  and  the  copper  precipitated  by  sulphuretted 
hydrogen  from  the  boiling  solution.  The  sulphide  is  filtered  off  and  washed 
well,  and  the  filtrate  concentrated  to  small  bulk.  On  cooling,  the  glycocoll 
separates. 

CH2ClCOOH  +  NH3  — >  CH2NH2COOH  +  HC1. 

Monoclinic  crystals  ;  M.P.  232° — 236°  with  decomposition  ;  soluble  in 
4  parts  cold  water,  almost  insoluble  in  alcohol  and  ether.   (A.,  266,  295.) 


432 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Peepaeation  489—  Glycocoll  Ester  and  Glycine J  Anhydride  (Ethyl 
ester  of  amino-ethan  acid)  and  (2.5-diketopiperazine). 

NH2.CH2.COOC2H5  and 

.CO — CH2X 

HN<  )NH.       (C4H902N  and)C4H6N202.       (103  and)  114. 

\CH2— CO/ 

Glycocoll  Ester. — 50  gms.  (1  mol)  gylcocoll-ester  hydrochloride  (see 
p.  395)  are  treated  with  25  c.cs.  of  water,  which  only  suffice  for 
partial  solution.  100  c.cs.  ether  are  then  added,  and  the  whole  well 
cooled  in  a  freezing  mixture  and  treated  with  40  c.cs.  (excess)  of  sodium 
hydroxide  (33%).  Finally,  such  an  amount  of  dry,  granulated  potassium 
carbonate  is  added  with  cooling  and  shaking  as  to  form  a  thick  paste. 
After  vigorous  shaking,  the  ethereal  solution  is  poured  off,  the  residue 
is  shaken  two  or  three  times  with  ether,  and  the  united  extracts,  after 
filtration,  are  allowed  to  stand,  with  frequent  shaking,  first  for  ten 
minutes  with  dry  potassium  carbonate  and  then  for  several  hours  with 
anhydrous  sodium  sulphate.  The  ether  is  evaporated  and  the  residue  is 
distilled  under  diminished  pressure.  At  10  mms.  it  boils  at  51-5° — 52-5°, 
and  so  the  receiver  must  be  well  cooled. 

NH3Cl.CH2COOC2H5  +  NaOH  =  NH2.CH2COOC2H5  +  NaCl  +  H20. 

Yield. — 65%  theoretical  (25  gms.)  B.P.718  148°— 149°.  with  decomposi- 
tion.   (A.,  127,  97  ;  J.  pr.,  [2],  37,  166.) 

Glycine  Anhydride. — 20  gms.  (2  mols.)  of  glycine-ester  are  cooled  and 
treated  with  12  gms.  of  water,  and  the  mixture  is  then  allowed  to  stand 
at  room  temperature  for  some  days.  The  anhydride  separates  out  during 
this  time  in  beautifully  crystalline  form.  It  is  filtered,  washed  with  a  little 
cold  water,  and  dried  under  reduced  pressure  over  sulphuric  acid. 

/CO— CH2 

2NH2CH2COOC2H5  =  HN\  >NH  +  2C2H5OH. 

XCH2— CO 

Yield. — 60%  theoretical  (7  gms.)  Colourless  plates  ;  turns  brown  at 
245°  ;  melts  with  blackening  at  275°.  Sublimes  on  rapid  heating.  (J.  pr., 
[2]  37,  173.) 

For  the  direct  preparation  of  glycine-anhydride  from  glycocoll  ester 
hydrochloride  see  B.,  39,  2930. 

Peepaeation  490. — Racemic  Phenylalanine  (3-Phenyl-2-amino-propan- 
acid). 

C6H5.CH2.CH(NH2).COOH.       C9Hn02N.  165. 

50  gms.  (1  mol.)  of  benzylmalonic  acid  (see  p.  235)  are  dissolved 
in  250  gms.  of  dry  ether,  and  50  gms.  (1^  mols.)  bromine  are  gradually 
added  in  daylight.  At  first  the  halogen  rapidly  disappears,  and  clouds  of 
hydrobromic  acid  are  evolved.  At  the  end  the  liquid  is  coloured  reddish- 
brown  by  the  excess  of  bromine.  When  it  has  stood  for  half  an  hour  the 
ethereal  solution  is  shaken  with  a  little  water,  sulphuric  acid  being 
gradually  added  until  the  red  colour  of  the  bromine  disappears.  The 


MISCELLANEOUS  PREPARATIONS 


433 


ethereal  layer  is  then  separated,  again  washed  with  a  little  water,  and 
carefully  evaporated.  The  solid  residue  is  recrystallised  from  about 
250  c.cs.  of  hot  benzene.  Yield,  95%  theoretical  (65  gms.).  The  benzyl- 
brommalonic  acid  when  dried  under  reduced  pressure  at  80°  melts  at 
137°  (corr.). 

The  benzylbrommalonic  acid  containing  water  is  now  heated  in  an  oil 
bath  to  125° — 130°,  and  the  fused  mass  evolves  carbon  dioxide  and  a 
certain  amount  of  hydrobromic  acid.  The  reaction  is  complete  in  the 
course  of  30 — 45  minutes.  The  residue  is  a  yellow  oil,  which  even  at  a  low 
temperature  does  not  crystallise,  and  which  in  the  main  consists  of 
phenyl- a-brompropionic  acid.  For  the  purpose  of  purification  it  is  washed 
with  water,  taken  up  in  ether,  and  dried  with  anhydrous  sodium  sulphate  ; 
the  ether  is  then  distilled  off.  The  mobile,  almost  colourless  oil  remaining 
is  dissolved  in  5  times  its  volume  (excess)  of  25%  aqueous  ammonia, 
and  either  heated  for  3  hours  to  100°  in  a  sealed  tube  or  allowed  to  stand 
for  3  to  4  days  at  ordinary  temperature.  On  evaporation  of  the  ammo- 
niacal  solution  an  almost  colourless  residue  is  left,  and  this  chiefly  consists 
of  ammonium  bromide  and  phenylalanine.  On  boiling  with  absolute 
alcohol  the  amino-acid  is  left  undissolved  and  is  recrystallised  from  hot 
water. 

C6H5.CH2CH(COOH)2  +  Br2  =  C6H5CH2CBr(COOH)2  +  HBr. 
C6H5CH2CBr(COOH)2  ->  C6H5CH2.CHBrCOOH  +  C02. 
C6H5.CH2CHBr.COOH  +  2NH3  =  C6H5CH2.CH(NH2)COOH  +  NH4Br. 

Yield. — 55%  theoretical  (24  gms.)  Colourless  crystals  ;  soluble  in  hot 
water.   M.P.  263°— 265°  with  decomposition.   (B.,  37,  3064.) 

Pkeparation  491. — Diazobenzene  Sulphonic  Acid  (Inner  salt  o!  diazo- 
nium  benzene  hydroxide-4-sulphonic  acid). 

/N  =  N 

[1  :  4]C6H4<      /  C6H4OaNaS.        168.  . 

20  gms.  (1  mol.)  of  sulphanilic  acid,  previously  dried  on  a  water  bath 
and  finely  powdered,  are  dissolved,  in  the  heat,  in  58  c.cs.  (1  mol.)  of  2N 
sodium  hydrate  ;  and  the  solution  is  diluted  until,  on  cooling  to  50°,  no 
crystallisation  occurs.  This  solution  is  now  treated  with  10  gms.  (rather 
more  than  the  calculated  amount)  of  sodium  nitrite,  and  the  mixture  is 
poured,  with  constant  stirring,  into  an  excess  of  cold,  dilute  sulphuric  acid. 
In  a  short  time  the  diazo -compound  separates  out  as  a  white,  crystalline 
mass.  To  favour  crystallisation  the  liquid  is  cooled,  and  after  it  has  stood 
for  some  time  the  substance  is  filtered  off.  This  compound  can  be  kept  in 
the.  dry  state,  but  must  not  be  dried  at  100°.  In  dealing  with  the  dry  pro- 
duct care  is,  however,  always  necessary,  for  it  sometimes  explodes  violently 
when  rubbed. 

>N  =  N 

C6H4(NH2)(S03H)  ->  C6H4(N  :  NC1)(S03H)  ->  C6H4<  / 

\so2 

Yield. — 80%  theoretical  (16  gms.).  Colourless  crystals ;  stable  enough 
to  be  recrystallised  frorcf  water  at  60°. 


s.o.c. 


434  SYSTEMATIC  ORGANIC  CHEMISTRY 


Preparation  492. — Diazomethane. 

CH2N2.  42. 

1.  Methylurethane  is  prepared  from  methylamine  and  chloroformic  ester. 

CICOOEt  +  NH2CH3  =  CH3NHCOOEt  +  HCL 

2.  Nitrosomethylurethane  is  prepared  by  treating  methylurethane  with 
a  mixture  of  sodium  nitrite  and  sulphuric  acid.  But  if  large  quantities 
are  required  it  is  better  to  lead  nitrous  fumes  (see  p.  509)  into  pure  methyl- 
urethane diluted  with  an  equal  volume  of  ether  until  the  liquid  has  assumed 
a  dirty  colour.  The  whole  is  washed  with  water  and  soda,  dried  over 
anhydrous  sodium  sulphate,  and  distilled  under  reduced  pressure.  If 
required  for  diazomethane  this  is  not  necessary.  This  substance  attacks 
the  skin,  lungs  and  eyes.  It  seems  to  be  hydrolysed  to  diazomethane  in 
the  body. 

HN02  N0 
CH3NHCOOEt   >  CH3NCOOEt. 

One  part  (1 — 5  c.cs. ;  not  more  has  been  used  to  the  present)  of  the 
nitrosourethane  are  placed  in  a  flask  fitted  with  a  descending  condenser, 
30 — 50  c.cs.  of  pure  ether  and  1 — 2  parts  of  25%  methyl  alcoholic  potash 
are  poured  in.  The  flask  is  warmed  on  a  water  bath.  A  yellowish  vapour 
comes  over  and  soon  the  ether  begins  to  distil.  The  operation  is  continued 
until  the  remaining  ether  in  the  flask  is  colourless.  The  ethereal  solution 
is  yellow  even  at  3- -5%  concentration. 

NO 

CH3NCOOEt  +  KOH  ->  CH2N2  +  KHC03  +  C2H5OH. 

Yield. — 50%.  Yellow,  odourless,  poisonous  gas,  soluble  in  dry  ether. 
(B.,  27,  1888  ;  28,  855  ;  35,  897.) 


PART  III 


CHAPTER  XXXIII 

ORGANIC  ANALYSIS 

Detection  of  Elements  present  in  Carbon  Compounds. 

Carbon  and  Hydrogen. — Some  fine  copper  oxide  is  heated  in  a  porcelain 
crucible  for  a  few  minutes  to  drive  off  all  moisture,  and  afterwards  left  to 
cool  in  a  desiccator.  A  small  amount — 0-1 — 0-2  gm. — of  the  compound 
is  mixed  with  about  10  times  its  weight  of  the  dry  copper  oxide  and  placed 
in  a  dry,  clean  test  tube  10 — 12  cms.  long.  4 — 6  cms.  of  dry  copper  oxide 
are  then  added,  and  the  tube  closed  with  a  cork  carrying  a  delivery  tube 
bent  at  a  right  angle.  The  tube  is  supported  in  a  horizontal  position  and 
gradually  heated,  beginning  first  at  the  unmixed  copper  oxide  and  raising 
it  to  a  high  temperature  before  the  compound  is  appreciably  heated.  The 
oxygen  of  the  copper  oxide  acts  as  oxidising  agent,  and  if  the  compound 
contains  hydrogen,  water  collects  on  the  cooler  portions  of  the  tube  ;  if 
it  also  contains  carbon,  the  issuing  gas,  when  passed  into  lime  or  baryta 
water,  causes  turbidity. 

Nitrogen,  Halogens,  Sulphur  and  Phosphorus. — A  piece,  about  0  5  c.c. 
of  bright  sodium  or  potassium  is  placed  in  a  small,  hard  glass  test  tube 
about  8  cms.  long  and  1  cm.  in  diameter.  (In  testing  easily  volatile  com- 
pounds, a  longer  tube,  to  act  as  a  condenser,  should  be  used.)  The  end  of 
the  tube  is  gradually  heated  at  some  distance  above  a  small  flame  until 
the  sodium  (or  potassium)  just  melts.  The  tube  is  withdrawn  from  the 
flame,  and  a  small  quantity  of  the  compound  dropped  on  to  the  surface 
of  the  molten  metal.  Generally  a  brisk  reaction,  often  accompanied  by 
detonations,  takes  place,  and  when  this  subsides  the  end  of  the  tube  is 
gradually  heated  to  bright  redness,  at  which  it  is  maintained  until  decom- 
position is  complete,  and  any  excess  of  sodium  is  oxidised.  By  this  treat- 
I  ment  there  is  formed :  sodium  cyanide  if  nitrogen  is  present ;  sodium 
halide  if  halogen  is  present ;  sodium  sulphide  if  sulphur  is  present ;  per- 
haps, sodium  sulphocyanide  if  both  nitrogen  and  sulphur  are  present,  but 
when  sulphur  is  present,  an  excess  of  sodium  should  be  used  in  order  to 
prevent  the  formation  of  sulphocyanide.  While  still  hot,  the  tube  is 
plunged  into  10  c.cs.  of  distilled  water  contained  in  a  small  beaker  or  dish  ; 
by  this  the  tube  is  shattered,  and  alkali  metal  remaining  reacts  briskly,  a 
quantity  of  carbon  remains  suspended  in  the  liquid,  and  any  cyanide, 
halide,  sulphide  or  sulphocyanide  formed,  passes  into  solution.  The 
mixture  is  boiled  for  a  minute,  then  cooled  and  filtered  through  a  pre- 
viously wetted  filter  paper.    The  filtrate  should  be  water  clear ;  if  not 

435  f  f  2 


436  SYSTEMATIC  ORGANIC  CHEMISTRY 


the  fusion  must  be  repeated  and  more  care  taken  to  ensure  the  complete 
decomposition  of  the  organic  compound  by  longer  heating.  The  filtrate 
is  divided  into  portions  which  are  tested  as  follows  : — 

(a)  For  Nitrogen. — To  one  portion,  about  1  c.c.  of  ferrous  sulphate 
solution  and  a  few  drops  of  ferric  chloride  solution  are  added.  Hydroxides 
of  iron  are  precipitated.  (If  no  precipitation  occurs,  a  little  caustic  soda 
solution  must  be  added.)  The  mixture  is  boiled  for  1 — 2  minutes,  and  if 
alkali  cyanide — equivalent  to  nitrogen  in  the  original  compound — is 
present,  sodium  ferrocyanide  is  formed.  After  cooling  under  the  tap,  the 
alkaline  mixture  is  acidified  with  hydrochloric  acid,  which  dissolves  the 
precipitated  ferrous  and  ferric  hydroxides,  and  the  resulting  ferric  salt 
reacting  on  the  sodium  ferrocyanide  forms  Prussian  Blue.  Accordingly 
a  blue  or  bluish-green  precipitate  indicates  the  presence  of  nitrogen.  At 
times  a  blue  or  bluish-green  solution  is  obtained,  which  only  gives  a 
blue  precipitate  after  standing  a  few  hours,  or  perhaps  overnight.  (The 
addition  of  a  little  potassium  fluoride  is  often  very  helpful  in  bringing 
down  the  blue  precipitate.)  When  the  test  is  doubtful,  it  should  be 
repeated,  using  more  of  the  alkaline  solution,  or  if  the  compound  contains 
only  a  small  percentage  of  nitrogen,  it  may  be  necessary  to  repeat  the 
fusion,  using  a  larger  quantity  of  the  compound.  Compounds  (e.g.,  diazo- 
compounds)  which  evolve  nitrogen  at  moderate  temperature  generally 
fail  to  give  a  positive  reaction  by  this  method,  and  in  such  cases  nitrogen 
can  be  detected  by  heating  the  compound  with  cupric  oxide  in  an  atmo- 
sphere of  carbon  dioxide  after  the  manner  of  a  Dumas  determination  of 
nitrogen  (p.  450),  and  finding  amongst  the  products  a  gas  which  is  not 
absorbed  by  caustic  potash.  For  volatile  or  unstable  nitrogen  com- 
pounds, a  mixture  consisting  of  138  parts  of  ignited  potassium  carbonate 
and  72  parts  of  magnesium  powder  may  be  used  in  place  of  sodium  (or 
potassium).  Small  quantities  of  this  mixture  and  of  the  compound  are 
intimately  mixed  and  heated  in  a  glass  tube.  The  mass  is  extracted  with 
water,  filtered,  the  filtrate  made  alkaline  and  tested  for  cyanide. 

(b)  For  Halogens. — If  nitrogen  has  been  proved  absent  by  (a),  a  portion 
of  the  solution  is  acidified  with  nitric  acid,  and  silver  nitrate  added.  A 
curdy  white  or  yellow  precipitate  indicates  the  presence  of  a  halogen.  If 
nitrogen  is  present,  the  solution,  after  acidification  with  nitric  acid,  must 
be  boiled  until  all  hydrocyanic  acid  is  expelled  before  silver  nitrate  is 
added. 

Halogens  may  also  be  detected  by  Beilstein's  test. — A  piece  of  pure 
copper  oxide,  held  by  means  of  a  platinum  wire  around  it,  is  heated  in  a 
Bunsen  flame  until  it  ceases  to  colour  the  flame  green.  It  is  then  allowed 
to  cool,  and  a  little  of  the  compound  is  placed  on  it.  If,  on  heating  again, 
there  appears  a  bright  green  flame  accompanied  by  a  blue  zone  round  the 
oxide  (due  to  the  volatilisation  of  copper  halide),  the  presence  of  a  halogen 
is  indicated. 

A  third  test  for  the  presence  of  halogens  consists  in  heating  the  com- 
pound along  with  an  excess  of  pure  lime  in  a  glass  tube.  The  mass  is 
afterwards  extracted  with  water,  and  tested  with  silver  nitrate. 

(c)  For  Sulphur.— To  a  portion  of  the  alkaline  filtrate  a  few  drops  of  a 


ORGANIC  ANALYSIS 


437 


freshly  prepared  solution  of  sodium  nitroprusside  are  added.  A  violet  or 
purple  coloration  indicates  the  presence  of  sulphur. 

Other  methods — in  all  of  which  the  resultant  sulphate  is  precipitated 
with  barium  chloride — for  the  detection  of  sulphur  in  compounds,  are  : 
(a)  oxidation  with  sodium  peroxide  (see  p.  463)  ;  (6)  oxidation  with 
sodium  carbonate  and  potassium  nitrate  ;  (c)  oxidation  with  fuming  nitric 
acid  in  sealed  tubes. 

(d)  For  Phosphorus. — About  1  c.c.  of  the  alkaline  filtrate  is  heated 
with  3  c.cs.  of  cone,  nitric  acid  for  a  few  minutes.  To  this  solution  after 
cooling,  ammonium  molvbdate  solution  is  added,  and  the  whole  warmed. 
A  crystalline  yellow  precipitate  of  ammonium  phosphomolybdate  on 
standing,  indicates  the  presence  of  phosphorus. 

Other  methods  for  the  detection  of  phosphorus  involve  oxidation  to 
phosphoric  acid  by  means  of  (a)  sodium  peroxide  ;  (b)  sodium  carbonate 
and  potassium  nitrate  ;  (c)  fuming  nitric  acid  in  sealed  tubes. 

The  presence  of  phosphorus  may  also  be  ascertained  by  heating  the 
compound  with  magnesium  powder,  and  moistening  the  cold  product  with 
water,  whereby  phosphine  (recognised  by  its  smell)  is  liberated  from  the 
magnesium  phosphide. 

Metallic  Radicles. — The  organic  matter  in  the  compound,  is  destroyed 
either  (a)  by  heating  to  redness  for  some  time  in  contact  with  air  in  a 
quartz  or  porcelain  crucible,  or  (b)  by  oxidising  with  a  mixture  of  cone, 
nitric  and  sulphuric  acids.  After  decomposition  is  complete,  the  residue 
is  examined  by  the  usual  tests  for  inorganic  radicles.  In  (a)  volatile 
radicles  such  as  mercury,  arsenic  and  ammonium  will  be  lost. 


CHAPTER  XXXIV 


QUANTITATIVE  ESTIMATION  OF  CAKE  ON  AND  HYDROGEN 

The  principle  involved  is  the  complete  oxidation  of  these  elements  to 
carbon  dioxide  and  water.  A  weighed  quantity  of  the  substance  is  heated 
along  with  cupric  oxide  in  a  stream  of  air  or  oxygen,  and  the  carbon  dioxide 
and  water  formed  are  absorbed  separately  and  weighed.  From  these  data 
the  percentages  of  carbon  and  hydrogen  in  the  compound  are  calculated. 

Oxygen  and  Air  Supplies. — The  air  or  oxygen  used  is  purified  from 
acidic  or  aqueous  vapours,  as  otherwise  these  would  be  absorbed  along 
with  the  products  of  combustion  ;  this  purification  is  effected  by  passing 
the  gas  through  soda  lime  and  sulphuric  acid.  The  purified  gas  then 
enters  the  combustion  tube  and  carries  along  with  it  the  products  of  com- 
bustion, namely,  carbon  dioxide  and  water ;  the  mixture  of  gases  next 
enters  an  apparatus  containing  sulphuric  acid,  which  absorbs  the  water 
formed,  while  the  carbon  dioxide  is  carried  along  to  be  absorbed  in  an 
apparatus  containing  caustic  potash  solution.  In  order  to  convey  a  pre- 
liminary idea  of  the  apparatus  used  and  procedure  adopted,  the  following 
diagrammatic  representation  is  given. 


Soda  lime  to 
remove  C02 


H2S04  pumice 
to  remove  H20 


Oxygen 

Soda  lime  to 

H2S04  pumice 

supply 

remove  C02 

— > 

to  remove  H20 

H2S04  bubbler 
to  indicate 
rate  of  flow 
of  gas 


Glass  tube  con- 
taining CuO 
and  substance 
placed  in  com- 
bustion furnace 


H2S04 
pumice 
to  absorb 
H20 


KOH 

to 
absorb 
C02 


Guard  tube 
of  CaCl2  + 
soda  lime. 


These  gases  can  be  conveniently  supplied  from  tinned  iron  containers  by 
displacement  with  water.  Such  containers  should  have  a  capacity  of 
about  30  gallons,  and  when  once  filled  will  serve  for  several  combustions. 
In  case  the  laboratory  is  not  equipped  with  containers  of  this  type,  the 
gases  can  be  suitably  supplied  from  glass  aspirating  vessels,  and  the 
oxygen  may  be  generated  by  heating  potassium  permanganate.  Or,  the 
oxygen  may  be  supplied  direct  from  a  pressure  cylinder  provided  the  latter 

438 


ESTIMATION  OF  CARBON  AND  HYDROGEN  439 


is  equipped  with  two  gauges— one  to  register  the  pressure  in  the  cylinder, 
and  the  other  the  pressure  at  which  the  gas  is  delivered.  The  operating 
pressure  is  generally  from  1—4  lbs.  Oxygen  prepared  by  electrolysis 
must  not  be  used  in  the  method  here  described,  as  it  often  contains  as 
much  as  1%  of  hydrogen. 

Purifying  Apparatus.— There  are  several  forms  of  apparatus  in  use, 
most  of  which  give  good  results  when  properly  manipulated.  The  follow- 
ing (Fig.  55)  is  simple,  and  gives 
excellent  results.  It  consists  of  two 
pairs  of  large  U  -tubes,  which  are  fixed 
by  wiring  to  a  wooden  stand.  They 
are  so  arranged  that  oxygen  can  be 
passed  through  one  pair,  and  air 
through  the  other.  The  outlet  from 
the  second  tube  of  each  pair  is  joined 
to  a  T-piece.  The  connections  are 
made  by  means  of  glass  tubes  and 
well-fitting  rubber  stoppers.  In  case 
any  connections  are  made  with  rubber 
tubing,  it  should  be  thick  walled,  and 
should  be  pushed  over  the  glass  tubes  until  they  meet.  In  order  that  one 
filling  will  serve  for  several  combustions  large  U -tubes,  3  cms.  internal 
diameter  and  15  cms.  high,  are  used.  The  first  of  each  pair  is  filled  with 
soda  lime,  and  the  second  with  pumice  moistened  with  pure  cone,  sul- 
phuric acid.  The  pumice  and  soda  lime  should  be  sifted  free  from  powder 
and  should  be  12 — 20  mesh  size.  As  pumice  occasionally  contains  calcium 
carbonate,  it  should  be  treated  with  hydrochloric  acid,  well  washed,  and 
dried  before  being  placed  in  the  U -tubes.  As  cone,  sulphuric  acid  often 
contains  oxides  of  nitrogen,  it  is  important  to  use  pure  acid,  and  then  only 
as  much  of  it  as  will  moisten  the  pumice.  In  order  to  prevent  dust  being 
carried  over  into  the  glass  delivery  tubes,  a  layer  of  absorbent  cotton  or 
asbestos  is  placed  over  the  soda  lime  in  the  limbs  of  the  tubes  which  con- 
tain it.  The  entrance  of  each  gas  to  the  purifying  train  is  controlled  by  a 
screw  pinchcock  on  the  rubber  tubing,  which  connects  each  gasholder  to 
the  purifying  train. 

Granular  (but  not  fused)  calcium  chloride,  or  aluminium  oxide  on 
pumice,  can  be  used  instead  of  sulphuric  acid  pumice  as  drying  agent. 
These  should  be  sifted  free  from  powder  and  filled  into  a  larger  U-tube, 
after  the  manner  in  which  the  soda  lime  tube  is  filled.  Whatever  reagent 
is  selected  here  for  drying  the  air  and  oxygen,  should  also  be  used  for 
absorbing  the  water  formed  in  the  combustion.  In  other  words,  the  dry- 
ing agents  used  in  each  instance  should  have  the  same  absorption  capacity. 
However,  owing  to  the  fact  that  commercial  calcium  chloride  often  con- 
tains basic  substances  which  absorb  carbon  dioxide,  the  use  of  sulphuric 
acid  pumice  is  preferable. 

Gas  Bubbler. — The  object  of  the  bubbler  is  not  only  to  give  an  idea 
as  to  how  fast  the  gas  is  passing  through  the  apparatus,  but  also  to  enable 
a  comparison  to  be  made  between  the  amount  of  gas  entering  the  combus- 


440  SYSTEMATIC  ORGANIC  CHEMISTRY 


tion  tube  and  the  amount  entering  the  potash  apparatus.   A  convenient 
form  of  bubbler  is  shown  in  Fig.  56.    It  is  attached  by  means  of  thick 
walled  rubber  tubing  to  the  T-piece  of  the  purifying 
<=^,  apparatus  and  contains  a  few  drops  of  pure  cone. 

QjZJ         sulphuric  acid. 

Fig.  56.  Combustion  Tube  and  Furnace. — The  type  of  furnace 

generally  used  consists  essentially  of  a  series  of  Bunsen 
flames  impinging  on  an  iron  or  nickel  trough  lined  with  asbestos  which 
serves  as  a  bed  for  the  combustion  tube.  While  the  gas  is  supplied  from 
a  common  main,  each  burner  is  so  constructed  that  its  air  and  gas  supply 
can  be  independently  regulated.  Above  the  tube  a  row  of  fireclay  tiles, 
to  serve  as  muffles,  are  arranged  so  as  to  regulate  the  temperature  and 
assist  in  the  heating  of  the  various  parts  of  the  tube.  Though  their  use 
has  not  yet  become  general,  electrically  heated  furnaces  may  be  used ;  the 
principle  is  the  same  as  that  of  the  gas  furnace,  namely,  that  they  consist 
of  a  series  of  heating  units,  each  of  which  can  be  controlled  by  its  own 
rheostat.  Such  a  furnace  has  advantages  over  the  gas  furnace  since  it  is 
cleaner  and  does  not  render  the  atmosphere  unpleasant  either  by  radiated 
heat  or  by  products  of  combustion.  The  length  of  the  combustion  furnace 
should  be  70— 75  cms. 

The  combustion  tube  should  be  of  difficultly  fusible  glass,  10 — 15  mms. 
internal  diameter  and  walls  1-5  mm.  thick.  It  should  be  cut  of  such  a 
length  that  it  projects  at  least  5  cms.  beyond  the  furnace  at  either  end. 
In  order  that  the  sharp  edges  of  the  tube  may  not  cut  the  rubber  stoppers, 
the  extreme  ends  are  heated  first  in  a  smoky  and  afterwards  in  a  blowpipe 
flame,  until  the  edges  are  just  rounded,  care  being  taken  to  avoid  any 
deformation  of  the  tube.  After  cooling,  the  tube  Is  washed  thoroughly 
and  dried. 

Cutting  Hard  Glass  Tubing.— To  cut  hard  glass  tubing  a  deep  file  mark 
is  made  at  the  desired  length.  Around  the  tube,  one  on  each  side  of  the 
file  mark,  are  folded  two  strips  of  wet  filter  paper.  These  rolls  of  paper  are 
moved  to  within  0-5  cm.  of  each  other  and  bound  on  the  tube  by  pieces 
of  cord.  The  space  between  the  rolls  of  paper  is  then  heated  in  a  small 
pointed  blowpipe  flame,  directing  the  flame  so  as  to  strike  only  the  top  of 
the  tube  while  the  latter  is  turned.  If  the  tube  does  not  crack  across  at 
first,  it  is  strongly  heated,  and  a  few  drops  of  water  from  a  tap  allowed  to 
fall  on  the  file  mark.   This  generally  effects  a  neat  cut. 

Filling  the  Tube. — The  simplest  case  of  combustion  is  that  involving 
the  analysis  of  a  substance  containing  carbon  and  hydrogen,  or  carbon, 
hydrogen  and  oxygen.  For  such  a  combustion  the  tube  is  filled  in  the 
following  manner  (Fig.  57).  A  loose  plug  of  asbestos,  or  a  spiral  of  copper 
gauze  0-5  cm.  wide  is  placed  in  the  tube  5  cms.  from  one  end  ;  coarse 
copper  oxide  (about  10  mesh  size)  or  "  wire  form  "  copper  oxide  is  poured 
in  through  a  wide  funnel  from  the  other  end  of  the  tube  until  there  is  a 
layer  about  45  cms.  long.  A  second  plug  of  asbestos  or  narrow  spiral  of 
copper  gauze  is  introduced  to  keep  this  copper  oxide  in  position.  A  spiral 
of  copper  oxide  is  prepared  by  rolling  tightly  a  strip  of  copper  gauze 
(40  mesh)  15  cms.  wide  round  a  stout  copper  wire  until  the  roll  neatly  fits 


ESTIMATION  OF  CAKBON  AND  HYDROGEN  441 


the  tube.  The  projecting  ends  of  the  wire  are  bent  into  loops  close  to  the 
gauze,  and  the  spiral  oxidised  by  heating  strongly  in  a  blowpipe  flame. 
When  cold  the  spiral  is  pushed  into  the  tube  to  a  distance  of  5  cms.  from 
one  end,  the  loops  enabling  it  to  be  moved  backwards  and  forwards  in  the 
tube  by  means  of  a  stout  hooked  copper  wire.  The  combustion  tube  is 
fitted  with  two  good  red  indiarubber  one-holed  stoppers  ;  these  should 
fit  accurately,  and  the  parts  which  come  into  contact  with  the  glass  should 
be  smeared  with  the  faintest  trace  of  vaseline  to  prevent  sti clang  to  the 


Fig.  57. 


tube  when  hot.  The  stopper  next  the  copper  oxide  spiral  carries  a 
glass  delivery  tube  ;  this  tube  is  provided  with  a  ground -glass  stopcock 
and  serves  as  inlet  for  the  purified  air  and  oxygen.  In  case  wire-form  copper 
oxide  is  used  the  tube  should  be  tapped  horizontally  on  the  bench  to  make 
a  passage  for  the  gas.  Care  should  also  be  taken  that  the  asbestos  plugs 
are  not  too  tightly  packed. 

The  tube  is  now  laid  on  the  trough  of  the  furnace,  and  over  each  end 
projecting  beyond  the  furnace  a  square  of  asbestos  having  a  circular  hole 
in  the  centre  is  placed  ;  these  protect  the  rubber  corks  from  the  heat  of  the 
furnace  during  the  combustion. 

Absorption  Apparatus  for  Water.— Granular  (not  fused)  calcium 
chloride,  alumina  pumice  and  pumice  moistened  with  cone,  sulphuric  acid 
are  efficient  absorbents  for  water.  On  the  whole  the  last  mentioned  has 
the  most  advantages  when  used  as  depicted  in  the  apparatus  Fig.  58. 
The  apparatus  consists  of  a  U-tube,  one  limb  drawn  out,  bent  at  a  right 
angle  and  sealed  to  a  bulb  tube  ;  the  other 

limb  is  open  as  shown  by  dotted  lines  at   ° 

E,  and  carries  a  side  tube,  F.  The  bend  ^  ^ 
and  parts  of  the  limbs  of  the  tube  are 
filled  with  pumice  (sieved  and  purified) 
moistened  with  cone,  sulphuric  acid.  A 
wad  of  asbestos  is  arranged  above  the 
pumice  in  limb  E.  This  done,  the  open 
end  E  is  wiped  dry  and  sealed  off  as 
shown.  During  the  combustion  the  side 
tube  0  is  in  position  through  the  cork  in  the  exit  end  of  the  combustion 
tube,  while  the  side  tube  F  is  connected  to  the  potash  absorbent 
apparatus  by  means  of  rubber  pressure  tubing.  At  other  times  the 
two  side  tubes  0  and  F  are  closed  by  pieces  of  rubber  pressure  tubing 
2  cms.  long  in  each  of  which  is  inserted  a  glass  rod  rounded  at  both 
ends  and  1 — 1-5  cm.  long.  It  is  important  that  the  edges  of  all  glass  tubes 
to  be  joined  by  rubber  connections  should  be  rounded  in  a  flame.  After 


Fig.  58. 


442  SYSTEMATIC  ORGANIC  CHEMISTRY 


about  twelve  combustions,  when  this  apparatus  becomes  inefficient 
through  the  absorption  of  water,  the  water  in  the  bulb  is  poured  out  through 
the  side  tube  0  and  D,  and  dried  by  means  of  folded  filter  paper  ;  cone, 
sulphuric  acid  is  introduced  from  a  pipette  through  the  side  tube  F,  and 
after  inclining  the  tube  so  as  to  "  wash  "  all  the  pumice,  the  acid  is  poured 
out  through  F.  When  this  operation  is  repeated  twice  and  F  dried  by 
means  of  folded  asbestos  paper,  the  apparatus  is  ready  for  further  use. 

When  calcium  chloride  is  used  as  absorbent  it  is  placed  in  a  U-tube 
similar  to  that  just  described.  Since  calcium  chloride  often  contains  basic 
chlorides  which  absorb  carbon  dioxide,  a  stream  of  dry  carbon  deoxide 
should  be  passed  through  the  filled  U-tube  for  2  hours  before  use  in  order 
to  neutralise  any  basic  substances  present.  The  excess  of  the  gas  is 
afterwards  driven  out  by  means  of  a  current  of  dry  air. 

Absorption  Apparatus  for  Carbon  Dioxide.— Several  forms  of  potash 
apparatus  are  in  use.  That  of  Geissler  (Fig.  59)  is  perhaps  the  most 
commonly  employed,  though  the  apparatus  (Fig.  60),  since  it  is  not  so 

liable  to  breakage  and 
also  since  it  contains 
four  bubbling  com- 
partments, is  more 
durable  and  efficient. 
The  bulbs  in  each 
case  are  filled  with  a 
solution  of  caustic 
potash  containing  50 
gms.  potash  to  50 
FIG>  59.  Fig.  60.  c-cs.  of  water.  Caus- 

tic soda  is  not  used 

owing  to  the  sparing  solubility  of  sodium  carbonate  in  caustic  soda 
solutions.  The  removable  side  tube  is  filled  with  granular  calcium 
chloride,  and  has  a  loose  plug  of  cotton-wool  at  each  end.  In  order  to 
fill  the  bulbs  with  potash  solution  the  side  tube  is  removed  and  a  length 
of  rubber  tubing  attached  in  its  stead  ;  the  other  end  of  the  apparatus  is 
dipped  into  a  basin  containing  the  potash  solution,  suction  is  applied,  until 
a  quantity  of  liquid,  almost  sufficient  to  fill  the  bulbs,  is  transferred.  After 
filling  the  bulbs,  that  part  of  the  apparatus  immersed  in  the  potash 
solution  is  dried  with  pieces  of  rolled  filter  paper,  the  ground-glass  joint  of 
the  calcium  chloride  tube  is  smeared  with  vaseline  and  the  side  tube 
replaced.  Stoppers  of  pressure  rubber  tubing  and  glass  rod  are  attached, 
and  these  are  only  removed  when  the  apparatus  is  in  use.  When  in  use, 
the  arm  tube  is  joined  by  pressure  rubber  to  a  straight  calcium  chloride 
guard  tube  and  the  other  end  is  similarly  joined  to  the  sulphuric  acid 
pumice  U-tube.  As  both  types  of  apparatus,  but  particularly  the  Geissler, 
are  fragile,  it  is  most  important  when  making  the  rubber  connections  to 
grip  the  apparatus  by  the  glass  tube  over  which  the  rubber  is  about  to  be 
pushed ;  any  pressure  across  the  bulbs  is  thus  avoided.  The  passage  of 
rubber  is  rendered  easier  by  breathing  on  the  glass  tube.  In  connecting 
the  apparatus  the  importance  of  using  rubber  pressure  tubing  and  of 


ESTIMATION  OF  CAKBON  AND  HYDROGEN  443 


bringing  the  ends  of  the  glass  tubes  closely  together  may  be  gathered  from 
Leiben's  remark,  "  that  if  long  rubber  tubes  are  employed  the  effect  is 
almost  the  same  as  if  the  gas  had  been  bubbled  through  water  again." 
The  potash  solution  should  be  renewed  after  every  two  combustions. 

Guard  Tube  of  Calcium  Chloride  and  Soda  Lime.— This  consists  of  a 
straight  calcium  chloride  tube,  one  half  filled  with  calcium  chloride  and  the 
other  half  filled  with  soda  lime,  a  plug  of  cotton-wool  being  placed  at  each 
end  It  is  connected  to  the  arm  tube  of  the  potash  apparatus  when  the 
latter  is  in  use,  and  serves  to  prevent  the  entrance  of  acidic  or  aqueous 
vapours.  It  is  also  used  to  prevent  the  ingress  of  aqueous  or  acidic  vapours 
to  the  combustion  tube  when  the  latter  is  disconnected  from  the  absorption 
train.  Copper  oxide  is  hygroscopic  and  it  is  necessary  to  protect  it  from 
the  moisture  of  the  air. 

Having  prepared  all  the  apparatus  as  indicated  in  the  foregoing,  the  whole 
is  assembled  as  shown  in  Fig.  61. 

The  gas  bubbler,  as  well  as  the  absorption  train,  is  supported  by  wires 
suspended  from  a  horizontal  support.  This  removes  any  weight  from  the 
ends  of  the  combustion  tube,  and  consequently  prevents  bending  of  the 
heated  tube. 

At  this  stage  notice  is  taken  that  all  walls,  connections  and  supports 
fulfil  the  conditions  already  specified. 

The  absorption  apparatus  is  then  disconnected  from  the  combustion 
tube  and  its  stoppers  of  rubber  tubing  and  glass  rod  replaced.  The  rubber 
stopper  in  the  exit  end  of  the  combustion  tube  is  also  removed. 

Preliminary  Heating  of  the  Combustion  Tube.— Air  is  turned  on,  and 
its  rate  of  flow  adjusted  so  that  2  or  3  bubbles  per  second  pass  through  the 
bubbler.  The  gas  jets  under  the  combustion  tube  are  lighted  and  gradually 
turned  up  until  the  tube  attains  a  dull  red  heat,  at  which  it  is  maintained 
for  about  an  hour,  the  tiles  being  in  position  over  the  tube.  In  this  way 
any  organic  impurities  are  oxidised  and  removed  along  with  any  moisture 
present  in  the  tube.  At  the  beginning  of  the  heating  moisture  condenses 
in  the  open  end  of  the  tube,  due  to  the  fact  that  copper  oxide  is  hygroscopic. 
The  greater  quantity  of  this  moisture  can  be  removed  with  a  piece  of 
folded  filter  paper.  As  soon  as  moisture  has  ceased  to  collect  the  open 
end  is  closed  by  its  cork  bearing  the  straight  calcium  chloride-soda  lime 
tube.  After  about  20  minutes'  further  heating  the  burners  are  turned  down 
and  finally  extinguished,  and  the  current  of  air  cut  off. 

Weighing  the  Absorption  Apparatus  prior  to  Blank  Experiment. — A 
cardboard  box  or  large  beaker  half  filled  with  cotton-wool  should  be  used 
to  carry  the  absorption  apparatus  from  one  room  to  another,  as  by  this 
means  the  dangers  of  breakage  and  contamination  by  grease  are  largely 
avoided.  While  the  combustion  tube  is  cooling  the  absorption  apparatus 
is  removed  to  the  balance  room,  wiped  free  from  dust  and  grease  with  a 
clean  cloth  which  is  free  from  lint  and  does  not  contain  sizing  or  starch. 
After  standing  30  minutes  inside  the  balance  case  the  stoppers  are  removed 
and  each  member  separately  weighed.  The  weighing  should  be  done 
quickly  and  the  stoppers  replaced. 

Blank  Experiment. — The  guard  tube  is  removed  from  the  combustion 


Hi  SYSTEMATIC  ORGANIC  CHEMISTRY 


tube  and  the  entire  absorption  train  connected  as  shown  in  Fig.  61. 
Before  proceeding  with  any  quantitative  experiments  it  is  necessary  to 
make  certain  that  the  apparatus  is  airtight.  To  do  this,  a  piece  of  stout 
rubber  tubing  carrying  a  screw  clip  is  affixed  to  the  exit  limb  of  the  potash 
apparatus.  The  screw  clip  is  not  closed  at  first.  A  stream  of  air  is  turned 
on,  and  if  it  bubbles  freely  at  the  same  rate  through  the  bubbler  and 
potash  bulbs  it  is  certain  there  is  no  undue  obstruction  to  the  passage  of 
gas  through  the  apparatus.  The  screw  clip  attached  to  the  potash  appara- 
tus is  then  closed  and  the  full  pressure  of  the  air  gradually  turned  on. 
After  the  first  few  bubbles  of  air  have  passed  through  the  potash  apparatus, 
no  further  movement  of  gas  should  appear  in  any  part  of  the  apparatus. 
If  it  withstands  this  test  the  screw  clip  is  released,  and,  while  air  is  passed 
through  at  the  rate  of  2 — 3  bubbles  per  second,  the  tube  is  gradually  heated 
to  a  dull  red  heat  for  30  minutes.    The  absorption  train  is  disconnected 


Fig.  61. 


and  stoppered,  and  the  guard  tube  inserted  again  in  the  combustion  tube. 
The  burners  are  gradually  turned  down  and  the  absorption  apparatus 
weighed  according  to  the  scheme  already  outlined.  The  increase  in  each 
absorbent  should  not  exceed  0-0003  gm.  If  the  increase  is  greater  than 
this,  it  is  possible  that  the  copper  oxide  was  not  thoroughly  dehydrated 
at  the  commencement  of  this  blank  run.  A  second  blank  run  will  show 
whether  the  copper  oxide  has  been  completely  dehydrated  during  the  course 
of  the  first  blank  run.  If  necessary  a  third  "  blank  "  is  run.  In  case  the 
sulphuric  acid  pumice  absorbing  apparatus  continues  to  gain,  the  purifying 
apparatus  for  the  removal  of  water  is  probably  inefficient  and  should  be 
refilled.  If  the  potash  apparatus  loses  weight  the  calcium  chloride  arm 
tube  has  become  saturated  with  moisture  and  should  be  refilled.  Finally 
the  apparatus  is  tested  by  means  of  blank  experiments  until  all  sources  of 
error  are  traced  and  eliminated  ;  the  increase  or  decrease  in  the  weight 
of  the  absorption  apparatus  will  not  then  amount  to  more  than  the  error 
in  weighing. 

Weighing  the  Boat  and  Substance. — When  the  blank  experiments 
have  been  completed  the  combustion  tube  is  allowed  to  cool  with  the 
straight  drying  tube  inserted  in  its  exit  end.  During  this  time  the  boat  is 
prepared  and  the  substance  weighed  out  in  it.  A  porcelain,  or  preferably 
a  platinum,  boat  7  cms.  long  is  used.  It  should  be  treated  with  nitric 
acid,  washed  with  water,  heated  in  a  blast  flame  and  cooled  in  a  desiccator. 
When  cold,  it  is  weighed,  0-15  to  0-2  gm.  of  the  substance  to  be  analysed 


ESTIMATION  OF  CARBON  AND  HYDROGEN  445 


is  introduced  and  weighed  again.  It  is  then  replaced  in  the  desiccator 
which  is  carried  to  the  combustion  room.  In  general,  liquids  of  boiling 
point  above  170°  may  be  weighed  directly  in  the  boat. 

The  Combustion. — When  the  inlet  end  of  the  combustion  tube  is  cold, 
the  cork  at  that  end  is  removed  and  the  copper  oxide  spiral  withdrawn  by 
means  of  a  hooked  wire.  The  boat  is  pushed  into  the  tube  as  far  as  the 
coarse  copper  oxide,  the  spiral  is  replaced  and  the  cork  bearing  the  glass 
delivery  tube  with  stopcock  closed,  inserted.  The  straight  calcium 
chloride  tube  is  removed  from  the  exit  end  of  the  combustion  tube,  and  the 
absorption  train  connected  as  in  Fig.  61.  At  this  stage  the  apparatus  is 
again  tested  in  the  manner  already  described  to  make  sure  that  it  is  air- 
tight. After  closing  the  screw  pinchcock  which  admits  the  air  to  the 
purifying  train,  the  glass  cock  is  opened,  and  a  slow  stream  of  air — 2 — 3 
bubbles  per  second — is  admitted  to  the  tube  by  carefully  opening  the 
pinchcock.  Small  flames  from  the  burners  under  the  copper  oxide  are 
lighted,  beginning  with  those  at  the  exit  end  of  the  tube  and  lighting  one 
by  one  until  a  point  about  10  cms.  from  the  boat  is  reached.  Two  or  three 
burners  under  the  copper  oxide  spiral,  but  not  within  5  cms.  of  the  boat, 
are  also  lighted.  The  flames  from  these  burners  are  gradually  increased 
in  size  until  the  tube  above  them  attains  a  dull  red  heat  when  the  corre- 
sponding tiles  are  in  position.  Next  follows  that  part  of  the  operation 
the  successful  carrying  out  of  which  is  essential  in  order  to  obtain  accurate 
results,  namely,  the  gradual  combustion  of  the  substance.  Some  informa- 
tion as  to  how  the  substance  is  likely  to  behave  may  be  obtained  before- 
hand by  gently  heating  some  of  it  on  a  piece  of  platinum  foil  and  noticing 
if  it  is  easily  volatile  or  if  it  leaves  a  charred  residue  difficult  to  burn  off. 
Until  experience  in  this  portion  of  the  combustion  has  been  acquired,  the 
further  heating  should  be  done  very  slowly,  as  any  sudden  rush  of  vapour, 
which  might  lead  to  imperfect  combustion,  is  to  be  avoided.  The  remaining 
burners,  beginning  with  those  farthest  from  the  substance,  are  lighted  and 
gradually  turned  on.  The  first  indication  of  combustion  is  the  appearance 
of  moisture  on  the  exit  end  of  the  tube,  and  an  increase  in  the  speed  of  the 
gas  passing  through  the  potash  apparatus.  With  easily  volatile  substances 
the  boat  is  heated  at  the  beginning  by  means  of  hot  tiles,  brought  from  an 
already  heated  part  of  the  furnace.  The  heating  should  be  conducted  in 
such  a  way  that  the  gas  bubbles  in  the  potash  apparatus  can  easily  be 
counted ;  if  the  rate  exceeds  this  limit,  the  heat  on  the  substance  must  be 
reduced  either  by  lowering  of  flames  or  removal  of  tiles,  until  the  approved 
speed  is  again  reached.  When  the  combustion  is  nearly  finished,  that  is, 
when  the  rate  of  gas  passing  through  the  potash  apparatus  approximates 
to  that  in  the  bubbler,  the  stream  of  air  is  shut  off  by  closing  first  the  glass 
stopcock  and  then  the  screw  pinchcock.  A  stream  of  oxygen  is  immediately 
turned  on,  the  screw  pinchcock  admitting  it  being  first  opened  and  then 
the  glass  stopcock.  In  this  way,  any  back  diffusion  of  gas  from  the  com- 
bustion tube  to  the  purifying  train  is  avoided. 

The  passing  of  oxygen  often  results  in  an  increased  speed  of  bubbles  in 
the  potash  apparatus.   If  not  done  previously,  the  tiles  over  the  boat  ar 
now  closed  and  the  whole  tube  heated  to  dull  redness  until  all  moisture  is 


446  SYSTEMATIC  ORGANIC  CHEMISTRY 


driven  from  the  exit  end,  and  the  gas  issuing  from  the  apparatus  rekindles 
a  glowing  splinter.  The  tiles  over  the  boat  should  be  occasionally  raised 
and  notice  taken  if  any  carbon  (graphite)  remains  in  the  boat.  Many 
substances  have  a  carbon  residue  which  only  burns  off  very  slowly,  and 
of  course  the  heating  must  be  continued  until  combustion  is  complete. 
The  removal  of  moisture  from  the  tube  is  generally  a  matter  of  some 
difficulty,  but  it  may  be  greatly  accelerated  by  holding  a  very  small  flame 
or  hot  tile  beneath  the  moist  parts,  and  at  the  same  time  passing  an 
increased  current  of  gas  through  the  apparatus.  Care  must  be  taken  that 
there  is  no  danger  of  the  cork  in  the  tube  being  burnt,  and  it  should 
always  be  possible  to  hold  the  glass  surrounding  the  cork  between  the 
finger  and  thumb.  In  general  the  time  occupied  from  when  the  tube  is  first 
heated  until  all  traces  of  moisture  are  driven  over  into  the  absorption 
apparatus  is  60 — 75  minutes.  Volatile  substances,  which  must  be  heated 
more  cautiously,  and  those  which  leave  a  residue  of  carbon,  require 
longer  time. 

As  soon  as  the  combustion  is  complete,  the  burners  are  lowered,  and  the 
stream  of  oxygen  is  replaced  by  one  of  air  in  order  to  displace  oxygen  from 
the  absorption  apparatus.  After  about  20  minutes  the  absorption  appara- 
tus is  disconnected  from  the  combustion  tube  and  stoppered.  The  straight 
^uard  tube  is  again  introduced  into  the  exit  end  of  the  combustion  tube, 
the  burners  are  extinguished  and  the  stream  of  air  shut  off.  The  absorp- 
tion apparatus  is  wiped  free  from  dust,  etc.,  allowed  to  stand  30  minutes 
beside  the  balance  and  then  weighed.  From  the  difference  in  the  weights 
of  the  absorption  apparatus,  before  and  after  the  combustion,  the  per- 
centages of  carbon  and  hydrogen  are  calculated  from  the  following 
formulae  : — 


%  of  carbon      ==  ^ 

Weight  of  substance  11 

o/    ,r  \  Weight  of  HoO  101 

%  of  hydrogen  =  oi  Vivace    X  m 

The  error  for  each  element  should  not  exceed  0-2%. 

Discussion  oi  Results. — The  difficulty  of  obtaining  an  accurate  "  blank 
determination  "  reveals  how  liable  the  analysis  is  to  slight  errors.  Even 
in  the  best  conducted  analyses  it  is  found  that,  as  a  rule,  the  percentage 
of  carbon  is  a  little  low  owing  to  the  loss  of  moisture  from  the  potash 
apparatus,  whilst  the  hydrogen  is  a  little  high.  The  formation  of  carbon 
monoxide  without  complete  oxidation  to  carbon  dioxide  leads  to  an  error, 
as  the  carbon  monoxide  which  is  not  absorbed  by  the  potash  escapes  from 
the  apparatus.  If  low  results  are  being  obtained  for  carbon,  the  escaping 
gas  should  be  bubbled  through  palladious  chloride  solution  or  some  other 
reagent  which  detects  carbon  monoxide.  Substances  which  yield  carbon 
monoxide  readily  should  be  burnt  with  a  very  long  layer  of  copper  oxide. 

Modifications  of  the  Method  and  other  Notes. — The  combustion  may  also 
be  conducted  entirely  in  a  current  of  oxygen.  It  is  still  an  open  question 
whether  it  is  preferable  to  use  oxygen  from  the  beginning  or  only  towards 


ESTIMATION  OF  CAKBON  AND  HYDROGEN  447 


,'the  end  of  the  combustion.    Both  methods  lead  to  the  same  result,  though 

i  the  second  is  the  more  economical,  a  little  quicker  and  not  so  conducive  to 

;  the  formation  of  graphite. 

The  purification  required  for  the  oxygen  depends  on  the  impurities  con- 

!  tained  in  it,  and  these  again  vary  according  to  the  source  and  preparation 
of  the  gas.  For  instance,  oxygen  prepared  by  electrolysis  contains  gener- 
ally from  0-1 — -1%  of  hydrogen,  and  obviously  the  purification  already 

:  described  would  not  be  sufficient  when  electrolytic  oxygen  is  used.  Such 
oxygen  should  be  passed  through  a  tube  containing  copper  oxide  heated 
to  dull  redness.  This  tube,  a  piece  of  combustion  tubing  about  30  cms. 
long,  containing  a  roll  of  copper  oxide  gauze,  or  layer  of  copper  oxide, 
12  cms.  long,  is  inserted  between  the  oxygen  supply  and  the  purifying 
apparatus.  It  is  most  conveniently  heated  in  a  short  furnace  of  the 
regular  combustion  type,  but  if  this  is  not  available,  it  can  be  heated 
with  a  few  Ramsay  or  other  flat-flame  burners. 

Cerium  dioxide  on  pumice  acts  as  a  very  active  oxidising  agent,  and  a 
short  layer  of  it  placed  between  the  boat  and  the  copper  oxide  enables  the 
combustion  to  be  carried  out  in  a  much  shorter  time,  as  the  h  eating  may  be 
done  more  rapidly  without  danger  of  incomplete  combustion.  To  prepare 
this  cerium  dioxide  pumice,  enough  pumice  to  fill  5  cms.  of  the  combustion 
tube,  5  gms.  of  pure  cerium  nitrate  crystals  and  enough  water  to  cover  the 
pumice  are  heated  to  dryness  on  a  water  bath  in  a  dish.  When  used, 
this  is  first  placed  in  the  combustion  tube  ;  it  is  kept  in  position  by 

i  two  very  narrow  spirals  of  copper  gauze.  The  decomposition  of  the 
cerium  nitrate  to  cerium  dioxide  is  completed  by  heating  in  the  combustion 
furnace  with  oxygen  passing  through,  first  at  low  temperature,  until 
all  moisture  is  driven  off,  and  finally  at  dull  red  heat,  until  the  cerium 
nitrate  is  decomposed. 

Combustion  ol  Volatile  and  Hygroscopic  Substances. — If  the  substance 
is  hygroscopic,  the  boat  must  be  enclosed  and  weighed  in  a  dry  stoppered 
tube,  to  which  two  small  pieces  of  glass  have  been  fused, 
in  order  to  prevent  it  rolling  when  on  the  pan  of  the  balance.  /^V_ 
If  the  substance  is  a  volatile  liquid,  it  must  be  weighed  in  a  V_X"~ 
small  glass  bulb  (Fig.  62),  drawn  out  to  a  wide  capillary.      Fig.  62. 

JThe  bulb  is  first  weighed.     It  is  then  heated,  and  while 
still  hot,  the  capillary  end  is  immersed  in  the  liquid.     As  the  bulb 
cools,  the  air  inside  it  contracts,  and  some  liquid  is  drawn  into  the 
bulb.    If  sufficient  liquid  is  not  introduced,  the  operation  must  be 
repeated.    The  tube  is  then  sealed  and  re-weighed.    When  the  bulb  is 

^about  to  be  introduced  into  the  combustion  tube,  the  end  of  the  capillary 

i  is  filed  and  broken  off,  the  bulb  is  placed  in  the  boat  with  its  open  end 

i  elevated  and  directed  towards  the  exit  end  of  the  combustion  tube.  In 
the  combustion  of  a  moderately  volatile  substance,  such  as  naphthalene, 
the  heat  from  the  copper  oxide  spiral  is  sufficient  to  volatilise  the  greater 
part,  and  hence  it  is  only  necessary  to  light  the  burners  under  the  boat 

i  towards  the  end  of  the  combustion.    In  the  case  of  highly  volatile  sub- 
stances, a  combustion  tube  is  used  which  projects  at  least  15  cms.  beyond 
he  furnace  at  the  inlet  end.    The  boat  containing  the  bulb  is  placed  just 


448  SYSTEMATIC  ORGANIC  CHEMISTRY 


outside  the  furnace,  and  then  the  copper  oxide  spiral  in  contact  with  the 
boat.  A  Bunsen  flame  is  placed  under  the  spiral,  and  the  heat  from  it 
regulated  so  as  to  vaporise  the  substance  at  a  convenient  speed. 

Combustion  of  Substances  containing  Nitrogen. — A  modification  of  the 
foregoing  procedure  must  be  adopted  for  the  combustion  of  substances 
containing  nitrogen,  since  oxides  of  nitrogen  are  formed  to  some  extent, 
and  these  are  liable  to  be  absorbed  in  the  potash  solution.  A  spiral  of 
metallic  copper  is  introduced  into  the  exit  end  of  the  tube  and  this,  when 
red  hot,  reduces  the  oxides  of  nitrogen  with  the  liberation  of  nitrogen, 
which  passes  through  the  apparatus  unabsorbed.  The  first  plug  of 
asbestos  is  introduced,  not  5  cms.  but  15  cms.  from  the  exit  end  of  the 
combustion  tube,  and  this  space  of  1 5  cms.  is  reserved  for  a  reduced  copper 
spiral.  The  layer  of  copper  oxide  is  shortened  by  10  cms.,  but  no  other 
changes  are  made  in  the  filling  of  the  tube.  The  copper  spiral  is  prepared 
by  rolling  a  strip  of  copper  gauze,  about  13  cms.  wide,  round  a  copper  wire 
until  the  roll  neatly  fits  the  tube.  To  give  the  spiral  a  clean  metallic 
surface,  it  is  gripped  with  a  pair  of  crucible  tongs  and  heated  to  bright 
redness  in  a  somewhat  roaring  blowpipe  flame.  It  is  then  quickly  pushed 
into  a  stout  test  tube  containing,  in  addition  to  a  pad  of  asbestos  at  the 
bottom,  about  1  c.c.  of  pure  methyl  alcohol.  During  this  operation  the  test 
tube  should  either  be  supported  in  a  clamp,  or  wrapped,  in  a  duster  if  held 
in  the  hand.  The  methyl  alcohol  reduces  the  film  of  oxide  on  the  gauze, 
and  is  oxidised  at  the  same  time  to  formaldehyde.  The  vapours  from  the 
tube  should  be  lighted,  and  when  the  flame  recedes  within  the  tube,  a 
good  cork  bearing  a  delivery  tube  is  inserted  and  connection  made  to  a 
suction  pump.  Gentle  suction  is  applied  and  as  the  copper  spiral  is  still 
fairly  hot,  practically  all  the  remaining  alcohol  is  quickly  removed. 

After  a  time,  the  test  tube  and  its  contents  are  allowed  to  cool,  and  the 
spiral  removed  to  a  vacuum  desiccator  containing  calcium  chloride,  where 
it  is  kept  until  required  for  insertion  in  the  combustion  tube. 

It  is  important  to  carry  out  the  combustion  in  such  a  manner  that  the 
copper  spiral  is  not  oxidised  to  any  appreciable  extent.  The  preliminary 
heating  of  the  copper  oxide  is  performed  as  already  described,  but  the 
reduced  copper  spiral  is  put  in  position  last — just  before  connecting  the 
combustion  tube  to  the  absorption  apparatus. 

The  combustion  may  be  carried  out  in  either  of  the  following  ways — | 
(a)  The  same  burners  of  the  furnace  are  lighted  as  for  non-nitrogenous 
substances,  and  air  is  passed  in  until  no  more  water  collects  at  the  exit  end 
of  the  tube  ;  the  burners  under  the  reduced  copper  spiral  are  then  extin- 
guished, and  the  current  of  air  replaced  by  one  of  oxygen.  The  current 
of  oxygen  is  continued  until  a  glowing  splinter  is  rekindled  by  the  gas 
issuing  from  the  absorption  train  ;  the  oxj^gen  is  finally  displaced  from  the 
apparatus  by  air. 

(b)  The  glass  stopcock  on  the  inlet  end  of  the  combustion  tube  is  closed, 
and  the  combustion  is  performed  without  the  passage  of  either  air  or 
oxygen  through  the  tube.  Oxygen  is  only  admitted  towards  the  end, 
and  at  the  same  time  the  burners  under  the  reduced  copper  spiral  are 
extinguished.    The  operation  is  completed  as  indicated  in  (a).  Sub- 


ESTIMATION  OF  CARBON  AND  HYDROGEN 


449 


stances  which  have  a  difficultly  combustible  nitrogenous  residue  should  be 
previously  mixed  with  fine  copper  oxide. 

Combustion  of  Substances  Containing  Sulphur  or  Halogen.— The  com- 
bustion of  these  substances  is  carried  out  similarly  to  that  of  non-nitro- 
genous substances,  with  the  exception  that  half  of  the  layer  of  copper 
oxide  is  withdrawn  from  the  exit  end  of  the  tube  and  replaced  by  chips  of 
fused  lead  chromate.  The  lead  chromate  retains  the  sulphur  and  halogens 
as  lead  sulphate  or  lead  halide,  and  thus  prevents  them  reaching  the 
potash  apparatus.  The  following  precautions  must  be  taken  :  (a)  the 
lead  chromate  must  not  be  heated  so  strongly  as  the  copper  oxide,  other- 
wise it  fuses  to  the  glass,  causing  the  latter  to  crack  on  cooling  ;  (b)  the 
lead  chromate  above  the  last  three  burners  at  the  exit  end  of  the  combus- 
tion tube  should  not  be  heated  so  strongly  as  the  rest  of  the  layer,  since 
lead  sulphate  is  slightly  unstable  and  lead  halide  slightly  volatile  at  a  high 
temperature.  The  combustion  of  halogen-containing  substances  may  be 
carried  out  by  means  of  copper  oxide  alone,  if  a  silver  spiral  is  inserted  at 
the  exit  end  of  the  combustion  tube  in  order  to  retain  the  halogen. 

Metallic  Radicles. — When  a  metallic  radicle  is  present  in  an  organic 
compound,  it  is  advisable  to  destroy  the  organic  matter  by  ignition  before 
making  an  estimation  of  the  metal.  The 

organo  compounds  of  some  metals  on   

ignition  give  carbonates,  while  others  give  ^"^T  ^7 

oxides.     In  certain  cases  where  nitrogen 

is  present,  cyanides  are  formed.     The  FlG- 63- 

metal  in  the  residue  is  then  estimated  by 

the  ordinary  methods.  In  many  cases  the  ignition  of  an  organo-metallic 
compound  may  be  carried  out  concurrently  with  the  combustion  of  the 
compound.  For  this  purpose  a  special  type  of  boat  (Fig.  63),  is  advan- 
tageous. The  boat  is  made  of  transparent  quartz  tubing  drawn  out  at 
both  ends  and  upturned  ;  these  ends  provide  an  entrance  and  exit  for 
the  air  or  oxygen,  while  none  of  the  residue  is  carried  over  by  the 
current  of  gas.    (J.  C.  S.,  121,  1292.) 


s.o.c. 


G  G 


CHAPTER  XXXV 


QUANTITATIVE  ESTIMATION  OF  NITEOGEN- 

Dumas  Method. — The  substance  is  completely  burned  by  copper  oxide 
in  a  tube  filled  with,  carbon  dioxide  ;  the  nitrogen  evolved  is  collected  over 
caustic  potash  and  its  volume  measured  ;  while  the  carbon  and  hydrogen, 
being  oxidised  to  carbon  dioxide  and  water  respectively,  are  retained  by 
the  caustic  potash  solution. 

The  combustion  may  be  carried  out  in  two  ways — (a)  in  a  tube  sealed 
at  one  end,  the  carbon  dioxide  being  generated  from  materials  inside  the 
tube,  and  (6)  in  a  tube  open  at  both  ends,  the  carbon  dioxide  being  generated 
in  a  second  vessel  and  passed  into  the  combustion  tube.  Method  (a)  is 
the  more  convenient  when  estimations  are  only  conducted  occasionally, 
and  method  (b)  when  estimations  are  frequently  or  continuously  conducted. 

Method  (a). — 500  gms.  of  coarse  or  wire-form  and  100  gms.  of  fine 
copper  oxide  are  placed  in  a  nickel  and  a  porcelain  boat  respectively. 
The  first  is  heated  to  a  dull  red  heat  in  a  muffle  furnace,  and  the  second 
is  heated  over  a  Bunsen  flame.  While  they  are  heated,  the  combustion 
tube  is  prepared. 

A  combustion  tube,  80 — 85  cms.  long,  and  similar  to  that  used  for  the 
estimation  of  carbon  and  hydrogen,  is  selected.  A  glass  rod  is  sealed  to 
one  end,  and  the  tube  is  heated  near  this  end  in  a  blowpipe  flame  until  the 
glass  softens,  when  it  is  quickly  drawn  out.  Heat  is  again  applied  to  the 
shoulder  of  the  tube  until  the  glass  softens,  when  it  is  again  drawn  out. 
If  a  good  blowpipe  has  been  used,  and  the  glass  well  softened  each  time, 
only  a  small  capillary  should  now  emerge  from  the  shoulder  of  the  tube  ; 
this  is  sealed  off  close  to  the  shoulder  and  the  latter  rounded  by  alternately 
heating  it  and  blowing  into  the  open  end  of  the  tube.  The  sealed  end 
should  be  annealed  by  holding  it  in  a  smoky  flame  before  setting  it  aside 
to  cool  (see  p.  38).    When  cold,  it  is  thoroughly  washed  out  and  dried. 

The  coarse  and  the  fine  copper  oxide  are  now  allowed  to  cool  somewhat 
before  being  introduced  into  two  clean  dry  flasks,  which  are  closed  with 
ground-glass  stoppers,  or  corks  coated  with  tinfoil. 

When  the  tube  is  about  to  be  filled,  it  should  be  clamped  in  a  vertical 
position  at  the  side  of  the  bench,  and  at  a  suitable  height  for  filling.  A 
funnel  with  a  short  but  wide  stem  should  be  inserted  in  the  open  end  of 
the  tube  to  assist  in  the  filling. 

As  shown  in  Fig.  64,  sufficient  magnesite  to  fill  12—13  cms.  is  first 
placed  in  the  tube  ;  it  should  be  in  pieces  the  size  of  a  pea,  and  sifted  free 
from  powder  ;  dark  or  discoloured  grains  should  be  rejected.  It  is 
important  to  use  only  the  best  qualities  of  magnesite.  A  plug  of  asbestos 
is  then  inserted  and  pushed  home  with  a  long  glass  rod.    Enough  coarse 

450 


QUANTITATIVE  ESTIMATION  OF  NITROGEN  451 


SI 

2  T 


£  « 


v-  oT 

Sid 


Fig.  64. 


copper  oxide  is  then  poured  in  through  the  funnel  to  fill  approximately 
8  cms.  of  the  tube  ;  this  is  followed  by  a  2-cm.  layer  of  fine  copper  oxide. 
For  mixing  the  substance  with  fine  copper  oxide  it  is  convenient  to  use  a 
weighing  bottle  of  shape  indicated  in  Fig.  64a;  the  neck  should  be  small 
enough  to  enable  it  to  be  inserted  in  the  end  of  the  combustion  tube. 
Enough  fine  copper 
oxide  to  fill  about 
5  cms.  of  the  com- 
bustion tube  is 
placed  in  this  bottle, 
about  0-2  gm.  of  the 
powdered  substance 
to  be  analysed  is 
accurately  weighed 

out  from  another  weighing  bottle  (which  should  contain  the  approxi- 
mate quantity)  and  placed  on  top  of  the  copper  oxide  in  the  first  bottle ; 
some  more  fine  copper  oxide,  sufficient  to  cover  the  substance,  is 
added,  and  the  whole  gently  mixed  by  shaking  the  bottle  with  stopper 
inserted.  The  contents  are  now  poured  into  the  combustion  tube,  and 
the  bottle  "  rinsed  "  a  few  times  with  fine  copper  oxide,  the  "  rinsings  " 
being  poured  into  the  combustion  tube.  The  layer  of  fine  copper 
oxide  and  substance  should  be  approximately  10  cms.  in  length.  A 
30-cm.  layer  of  coarse  copper  oxide  is  then  poured  in,  and  an  asbestos 
plug  inserted  to  keep  it  in  position.  A  reduced  copper  spiral  10  cms.  long 
is  prepared  as  described  on  p.  448  ;  as  in  the  estimation  of  carbon  and 
hydrogen  in  nitrogenous  compounds,  it  serves  to  decompose  oxides  of 
nitrogen  with  the  liberation  of  free  nitrogen  ;  it  is  placed  in  position  as 
shown  in  Fig  64. 

Before  commencing  to  fill  the  tube,  the  subdivisions  should 
be  marked  off  on  it  against  a  meter  stick  ;  the  various  lengths 
should  not  differ  much  from  the  figures  given,  as  otherwise  the 
layer  of  coarse  copper  oxide  may  be  too  short  or  the  copper 
spiral  out  of  position.  When  the  tube  is  filled,  it  is  fitted  with 
a  good  rubber  stopper  carrying  a  bent  delivery  tube,  and  whilst 
placed  in  a  horizontal  position  on  the  bench,  it  is  gently  tapped 
along  one  side  in  order  to  make  a  passage  for  gas  above  its 
contents. 

The  tube  is  now  placed  in  a  furnace  possessing  a  flame  surface  of  75  cms. ; 
the  furnace  should  be  tilted  so  that  the  sealed  end  of  the  tube  is  somewhat 
higher  than  the  other,  and  the  5  cms.  free  space  should  just  lie  outside  the 
furnace.  This  arrangement  prevents  any  moisture  which  collects  in  the 
cooler  protruding  part  of  the  tube  from  running  back  into  the  hotter 
portion.  In  order  to  protect  the  rubber  stopper,  a  square  of  asbestos 
board,  having  a  circular  hole  in  the  centre,  is  placed  over  the  tube 
between  the  furnace  and  the  stopper. 

For  the  collection  of  the  nitrogen  a  graduated  SchifFs  azotometer  (Fig. 
65)  is  used.  Into  this  a  quantity  of  mercury  sufficient  to  fill  it  4 — 5  mms. 
above  the  lower  side  tube,  is  first  placed.    A  solution  of  potash,  previously 

G  G  2 


Fig.  64a. 


452  SYSTEMATIC  ORGANIC  CHEMISTRY 


prepared  by  dissolving  caustic  potash  (about  150  gms.)  in  an  equal  weight 
of  water  in  a  porcelain  dish,  is  then  poured  into  the  pear-shaped  reservoir. 
By  opening  the  tap  and  raising  the  reservoir,  the  apparatus  becomes  filled 
and  remains  so  on  closing  the  tap  and  lowering  the  reservoir.  The  tap 
should  be  greased  and  examined  to  see  that  it  is  thoroughly  air-tight. 
The  lower  bent  tube  of  the  azotometer  is  connected  to  the  delivery  tube 


Fig.  65. 


extending  from  the  combustion  tube  by  means  of  thick  pressure  rubber 
tubing  on  which  a  screw  pinchcock  is  placed. 

The  Combustion. — The  tap  of  the  azotometer  is  opened  and  the  pear- 
shaped  reservoir  lowered  so  that  it  contains  practically  all  the  potash 
solution.  The  pinchcock  is  opened,  leaving  the  apparatus  ready  for 
flooding  with  carbon  dioxide.  The  burners  under  the  one-half  of  the 
magnesite  layer  next  the  sealed  end  of  the  tube  are  lighted  and  gradually 
turned  on  until  the  flames  all  but  meet  over  the  tube ;  the  tiles  over  these 
burners  are  then  closed  down.  A  rapid  stream  of  carbon  dioxide  is  thus 
produced,  which  quickly  drives  the  air  out  of  the  tube  before  diffusion 
has  time  to  take  place. 

After  a  rapid  current  of  carbon  dioxide  has  been  evolved  for  ten  minutes, 
the  burners  under  the  spiral  and  the  layer  of  coarse  oxide  to  within  10  cms. 
of  the  fine  copper  oxide  are  lighted  in  order  to  drive  out  any  occluded  gases 
(hydrogen  and  air).  In  another  15  minutes  the  current  of  carbon  dioxide 
is  allowed  to  slow  down  a  little  ;  the  azotometer  is  filled  with  potash 
solution  by  raising  the  reservoir  and  closing  the  tap. 

The  gas  entering  the  azotometer  is  now  largely  absorbed  on  passing  up 
the  column  of  potash  ;  the  bubbles  should  decrease  in  size  as  they  ascend, 
and  appear  as  mere  specks  on  approaching  the  top.  If,  however,  this  is 
not  the  case,  owing  to  the  combustion  tube  still  containing  an  appreciable 
quantity  of  air,  the  tap  should  be  opened  and  the  reservoir  lowered,  and  a 
rapid  current  of  carbon  dioxide  passed  for  5  minutes  longer.    The  test  is 


QUANTITATIVE  ESTIMATION  OF  NITROGEN  453 


again  repeated  ;  if  after  2  minutes  only  a  trace  of  foam  has  collected,  the 
azotometer  is  filled  with  potash  solution,  the  tap  closed  and  the  reservoir 
lowered  as  far  as  possible.  The  current  of  carbon  dioxide  is  lessened,  all 
but  one  burner  under  the  magnesite  being  either  extinguished  or  lowered. 
The  copper  spiral  and  the  part  of  the  coarse  copper  oxide  already  heated 
should  now  be  at  a  dull  red  heat.  The  burners  under  the  coarse  oxide  on 
both  sides  of  the  fine  oxide  are  now  lighted,  beginning  with  those  farthest 
away  from  the  substance,  and  lighting  two  at  a  time — one  on  each  side. 

!  Each  burner,  the  tiles  above  it  being  closed,  should  heat  the  tube  above  it 
to  a  dull  red  heat  before  its  neighbour  is  lighted,  but  the  flames  should  not 
meet  above  the  tube.  When  the  flames  approach  the  fine  oxide  mixed 
with  the  substance,  the  gas  passing  into  the  azotometer  should  be  carefully 
watched,  and  as  soon  as  any  nitrogen  collects,  the  further  heating  of  the 

!  substance  should  be  done  very  gradually.  As  described  in  the  estimation 
of  carbon  and  hydrogen,  a  little  of  the  substance  should  be  examined 
beforehand  to  ascertain  whether  it  is  easily  volatile  or  not.  If  the  sub- 
stance  is  easily  volatile,  it  should  be  heated  at  first  with  very  small  flames 
or  with  hot  tiles  brought  from  an  already  heated  part  of  the  furnace.* 
The  success  of  the  analysis  largely  depends  on  the  gradual  heating  of  the 
substance ;  only  one  burner  at  a  time  should  be  lighted  under  the  sub- 
stance, and  when  the  amount  of  unabsorbed  gas  evolved  at  this  heat 
slackens,  another  burner  is  lighted.  The  rate  of  gas  bubbles  passing  up 
the  azotometer  should  not  be  greater  than  can  be  easily  counted  ;  irregular 
bursts  of  gas  may  cause  the  potash  solution  to  be  sucked  back  into  the 
combustion  tube.  When  the  substance,  having  been  heated  in  this 
fashion  up  to  a  dull  red  heat,  ceases  to  evolve  nitrogen,  the  burners  under 
the  magnesite  layer  are  lighted,  and  a  not  too  rapid  stream  of  carbon 
dioxide  passed  through  the  apparatus  for  about  15  minutes  in  order  to 
drive  all  traces  of  nitrogen  into  the  azotometer. 

The  absorption  apparatus  is  then  closed  by  the  pinchcock  and  discon- 
nected from  the  combustion  apparatus  at  the  rubber  tubing.  The  burners 
under  the  spiral  and  oxide  are  gradually  turned  down  so  that  the  combustion 
tube  cools  with  a  slow  stream  of  carbon  dioxide  passing  through  it ;  this 
prevents  the  copper  spiral  being  oxidised.  The  reservoir  is  raised  until 
the  liquid  in  it  is  at  the  same  level  as  the  liquid  in  the  azotometer  and  a 
thermometer  is  hung  beside  the  azotometer.  The  levels  of  the  liquid  in 
the  reservoir  and  azotometer  are  adjusted  occasionally,  and  in  about  an 
hour  the  volume  of  the  nitrogen  is  read  off,  and  the  temperature  and 
atmospheric  pressure  noted. 

The  percentage  of  nitrogen  is  calculated  from  the  formula  : — 

100        _   I  0-0012562 
w     (       P)  760(1  +  0-003665-0 

where  w  is  the  weight  in  grams  of  the  substance  taken,  V  the  observed 
volume  of  nitrogen,  P  the  barometric  pressure  in  mm.  of  mercury,  and 

*  If  the  carbon  dioxide  is  so  slowly  absorbed  that  it  tends  to„drive  the 
potash  out  of  the  azotometer,  fresh  potash  solution  should  be  placed  in  the 
cup  at  the  top  and  admitted  by  opening  the  stopcock  very  slightly. 


454  SYSTEMATIC  ORGANIC  CHEMISTRY 

p  the  vapour  pressure  of  the  potash  solution  at  the  temperature  t ;  when 
50%  potash  solution  is  used  its  vapour  tension  is  negligibly  small.  Instead 
of  reading  the  volume  of  nitrogen  in  the  azotometer  it  is  often  customary 
to  transfer  it,  after  all  traces  of  carbon  dioxide  have  been  absorbed,  to  a 
graduated  tube  standing  over  water.  This  gives  a  result  free  from  any 
errors  due  to  incorrect  vapour  tension  or  to  the  presence  of  foam  on  the 
surface  of  the  potash  in  the  azotometer.  When  it  is  intended  to  transfer 
the  nitrogen  after  this  fashion,  an  azotometer  having  a  delivery  tube  above 
the  tap  should  be  used  ;  a  truncated  funnel  is  attached  on  this  delivery 
tube  by  means  of  a  piece  of  rubber  tubing  or  cork  so  as  to  form  a  cup 
surrounding  the  delivery  tube  (Fig.  66).  At  the  time  the  azotometer  is 
filled  just  prior  to  the  collection  of  the  nitrogen  evolved  during  the  com- 
bustion, the  pear-shaped  reservoir  should  be  raised  sufficiently  high  to  fill 
the  delivery  tube  with  potash  solution.  To  transfer  the  nitrogen  the  cup 
at  the  top  of  the  azotometer  is  filled  with  water  above  the  end  of  the 
delivery  tube,  and  any  bubbles  of  air  in  the  delivery  tube  are  expelled  by 
allowing  water  to  enter  it  through  a  glass  tube  drawn  out 

Yto  a  capillary.  A  graduated  tube,  completely  full  of  water, 
is  closed  by  the  finger  and  inverted  in  the  water  in  the 
cup  in  such  a  position  that  the  end  of  the  capillary  enters 
the  mouth  of  the  graduated  tube.  The  nitrogen  is  expelled 
from  the  azotometer  by  raising  the  reservoir  and  opening 
the  stopcock.  The  graduated  tube  containing  the  nitrogen 
—  is  then  transferred,  after  closing  the  open  end  with  the 

4  finger,  to  a  long  glass  cylinder  containing  cold  water  ;  here 

it  is  clamped  and  allowed  to  stand  20  minutes  in  order  to 
^  attain  room  temperature.  The  volume  of  the  gas  is  read  off 

Fig.  66.  after  adjusting  the  tube  so  that  the  level  of  the  water  is  the 
same  inside  and  outside,  the  tube  being  held  with  a  wooden 
or  paper  holder,  but  not  with  the  hands.  The  barometric  pressure  is 
noted,  and  the  temperature  of  the  gas  is  taken  as  that  of  the  water  with 
which  it  is  in  contact.  The  percentage  of  nitrogen  is  calculated  from  the 
same  formula  as  before,  p  representing  the  vapour  tension  of  water  in 
this  case. 

A  third  method  of  measuring  the  nitrogen  is  to  let  it  remain  in  the 
azotometer  and  displace  the  potash  solution  by  water.  About  20  c.cs.  of 
potash  solution  is  placed  in  the  cup.  The  reservoir  is  lowered,  the  stop- 
cock is  partially  and  carefully  opened  to  allow  the  solution  from  the  cup  to 
run  down  the  inside  walls  and  absorb  any  traces  of  carbon  dioxide  that 
may  be  present.  The  stopcock  is  closed  before  all  the  solution  has  left 
the  cup.  The  operation  is  repeated,  using  cold  distilled  water  to  wash  the 
gas  until  the  potash  solution  is  out  of  the  azotometer  and  reservoir.  While 
the  potash  solution  is  being  displaced  into  the  reservoir  it  should  be 
poured  out  a  little  at  a  time,  care  being  taken  that  air  is  not  admitted  to 
the  azotometer  through  the  rubber  tube. 

Method  (b). — The  combustion  tube  used  is  in  every  way  similar  to  that 
used  in  connection  with  the  estimation  of  carbon  and  hydrogen. 

The  short  tube  (Fig.  67)  is  partially  filled  with  powdered  sodium  bicar- 


QUANTITATIVE  ESTIMATION  OF  NITROGEN 


455 


bonate  or  magnesite  in  pieces  the  size  of  a  pea,  and  a  loose  plug  of  glass-wool 
is  inserted  to  retain  solid  particles  ;  the  tube  should  be  tapped  horizontally 
to  provide  a  channel  for  gas  ;  it  is  heated  either  in  a  short  furnace  or  by  flat 
name  Bunsen  burners.  The  two  tubes  are  connected  by  rubber  stoppers 
and  a  trap  which  prevents  any  drops  of  moisture  arising  from  the  decom- 
position of  the  bicarbonate  from  passing  into  the  heated  combustion  tube. 
The  method  of  filling  the  combustion  tube  is  indicated  in  the  general 
diagram  (Fig.  67).  The  mixture  of  fine  copper  oxide  and  substance  is 
placed  in  a  long  boat  which  may  be  porcelain,  quartz  or  copper.  The 
copper  oxide  spiral  takes  the  place  of  the  short  layer  of  copper  oxide 
mentioned  in  method  (a)  and  serves  to  oxidise  any  vapours  which  diffuse 
backwards.  The  reduced  copper  spiral  is  inserted  after  the  rest  of  the  tube 
is  filled.  The  manner  of  connecting  the  combustion  tube  to  the  azotometer 
as  well  as  the  manner  of  conducting  the  combustion  is  the  same  as  described 
in  method  (a).  It  is  particularly  important  that  the  evolution  of  carbon 
dioxide  from  the  smaller  tube  should  not  cease  altogether  at  any  time,  since 
otherwise  vapours  may  diffuse  backwards  into  the  trap. 

The  convenience  of  this  method  for  carrying  out  a  number  of  consecutive 


"<-5cms-x7<:nis 


B  11  H=^g_^=(XE 


40cms- 


Fig.  67. 


estimations  is  obvious  ;  the  oxidised  spiral  can  be  quickly  removed  and 
replaced,  and  the  short  tube  can  be  quickly  recharged  and  connected. 
Before  starting  a  second  combustion,  however,  the  boat  and  the  reduced 
copper  spiral  should  be  removed  from  the  tube  and  a  current  of  dry 
oxygen  passed  through  while  the  tube  is  heated  to  dull  redness  for  about 
15  minutes  ;  any  reduced  copper  is  thus  reoxidised.  After  this  preliminary 
heating  the  tube  should  be  allowed  to  cool  in  a  current  of  dry  carbon  dioxide 
generated  from  a  Kipp  apparatus.  Copper  oxide  which  occludes  a  small 
quantity  of  air  when  heated  and  cooled  in  air  does  not  occlude  the  gas 
so  readily  when  cooled  in  carbon  dioxide. 

Length  of  Time  for  an  Analysis. — From  the  beginning  of  the  heating 
of  the  magnesite  to  the  appearance  of  a  rapid  current  of  carbon  dioxide 
requires  about  10  minutes  ;  the  first  test  as  to  whether  air  is  still 
present  in  the  tube  should  be  made  15  minutes  later ;  length  of  time  for 
further  tests,  5  minutes.  The  heating  of  the  spiral  and  coarse  oxide  to  dull 
redness  occupies  about  15  minutes  ;  further  heating  to  start  the  com- 
bustion of  the  substance  5  minutes.  The  combustion  proper  requires  30 
minutes.  Displacement  of  the  last  traces  of  nitrogen  by  heating  the 
magnesite  occupies  10  minutes.  The  total  time  required  for  these  periods 
of  heating  is,  therefore,  90  minutes. 

Further  Notes. — More  heating  is  required  to  generate  carbon  dioxide 


456  SYSTEMATIC  ORGANIC  CHEMISTRY 


from  magnesite  than  from  sodium  bicarbonate.  A  mixture  of  potassium 
bichromate  and  sodium  carbonate  has  been  recommended  for  the  genera- 
tion of  carbon  dioxide  by  direct  heating.  Manganese  carbonate  has  also 
been  recommended.  Carbon  dioxide  may  also  be  obtained  by  the  action 
of  acid  on  marble  in  a  Kipp  apparatus  ;  the  marble  must  be  previously 
boiled  for  a  long  time  with  water  to  expel  occluded  air,  and  even  then  it  is 
almost  impossible  to  get  rid  of  the  last  traces.  The  acid  should  also  be 
boiled. 

Sodium  hydroxide  should  not  be  used  in  the  azotometer  as  the  carbonates 
formed  crystallise  out  easily  owing  to  their  sparing  solubility  in  caustic 
soda  solutions. 

Cupric  oxide,  when  heated  and  cooled  in  an  atmosphere  of  air  or  oxygen, 
absorbs  some  of  these  gases  which  it  only  gives  off  very  slowly  when 
reheated  ;  this  causes  an  error  in  the  estimation  of  nitrogen.  With  com- 
pounds containing  much  nitrogen  the  percentage  error  due  to  this  cause 
is  very  small,  but  with  compounds  containing  little  nitrogen  the  error  is 
appreciable. 

The  Dumas  method  is  applicable  to  every  type  of  organic  nitrogen 
compound  and  gives  accurate  results.  In  a  few  cases  the  method  gives 
results  which  are  too  high  owing  to  the  formation  of  methane,  which  is 
not  completely  oxidised  by  copper  oxide  in  absence  of  oxygen,  and  collects 
in  the  azotometer.  To  obviate  this  difficulty  the  coarse  copper  oxide  should 
be  replaced  by  a  long  layer  of  lead  chromate  and  the  substance  mixed 
with  'fine  copper  oxide  and  powdered  lead  chromate.    (J.  C.  S.,  89,  570.) 

If  any  nitric  oxide  escapes  decomposition  by  the  reduced  copper  spiral 
its  presence  is  detected  when  the  gas  in  the  azotometer  is  mixed  with  air. 
Nitrogen  as  nitric  oxide  occupies  twice  the  volume  of  the  same  amount  of 
nitrogen  in  the  free  state. 

Kjeldahl's  Method  of  Estimating  Nitrogen. — The  majority  of  organic 
nitrogen  compounds  in  which  nitrogen  exists  in  a  non-oxidised  form,  when 
heated  with  concentrated  sulphuric  acid  are  completely  destroyed,  with 
formation  of  ammonium  sulphate.  Compounds  containing  methyl  groups 
attached  to  nitrogen  are  seldom  completely  destroyed,  but  give  rise  to 
methylamines  ;  this,  however,  causes  no  error,  since  the  methylamines 
are  strong  bases.  From  the  resulting  solution  the  ammonia  (or  methyl- 
amine)  is  liberated  by  means  of  alkali ;  the  gas  is  distilled  off  and  collected 
in  standard  acid. 

A  weighed  quantity — generally  about  0-5  gm.,  but  varying  from  0-2  gm. 
to  1-0  gm.,  according  to  the  percentage  of  nitrogen — of  the  finely  powdered 
substance  is  placed  with  about  10  gms.  of  pure  potassium  hydrogen 
sulphate  in  a  long-necked,  round-bottomed  Jena  flask  of  500  c.cs.  capacity, 
and  30  c.cs.  of  pure  concentrated  sulphuric  acid  are  introduced  from  a 
pipette.  The  object  of  the  potassium  hydrogen  sulphate  is  to  promote 
oxidation  by  raising  the  boiling  point  of  the  liquid.  The  flask  is  clamped 
over  a  sand  bath  and  the  contents  boiled  briskly  until  the  liquid,  which 
first  darkens  in  colour,  becomes  clear  and  colourless  or  slightly  yellow. 
At  this  stage  the  active  evolution  of  sulphur  dioxide  ceases.  This  initial 
decomposition  generally  requires  30 — 60  minutes'  heating.    Should  it 


QUANTITATIVE  ESTIMATION  OF  NITROGEN  457 


prove  difficult  to  effect,  pure  precipitated  manganese  dioxide  which  has 
been  dried  at  150°  is  added  in  small  quantities  to  the  hot  liquid  at  intervals 
of  about  3  minutes,  with  thorough  agitation  of  the  contents  of  the  flask 
after  each  addition,  until  a  pale  yellow  or  pink  colour  is  attained.  The 
oxidation  is  effected  very  rapidly  by  the  addition  of  the  manganese 
dioxide,  generally  not  occupying  more  than  15  minutes  when  the  mixture 
is  at  a  sufficiently  high  temperature.  Instead  of  adding  manganese 
dioxide,  a  crystal  (about  0-5  gm.)  of  copper  sulphate  or  a  drop  of  mercury 
may  be  added  to  serve  as  an  oxygen  carrier,  but  the  oxidation  is  not 
effected  so  quickly  as  when  manganese  dioxide  is  used. 

When  the  decomposition  is  complete  the  flask  is  allowed  to  cool,  the 
contents  are  diluted  with  2 — 3  vols,  of  dis- 
tilled water,  and  a  few  pieces  of  porous 
earthenware,  which  later  serve  to  induce 
regular  ebullition,  added.  The  flask  is  now 
attached  to  the  distilling  apparatus  shown 
in  Fig.  68.  Through  one  hole  of  the  doubly 
bored  rubber  stopper  a  bulb  adapter,  widen 
serves  to  retain  any  alkali  carried  upwards, 
is  inserted.  The  end  of  the  adapter  is  con- 
nected with  an  upright  condenser,  the  end 
of  which  just  dips  below  the  surface  of 
25  c.cs.  of  a  semi-normal  solution  of  hydro- 
chloric or  sulphuric  acid,  contained  in  a 
conical  flask.  A  tap-funnel,  bent  as  shown, 
is  inserted  in  the  neck  of  the  flask  through 
the  second  hole  in  the  cork.  A  solution 
containing  30  gms.  of  caustic  soda  in 
60  c.cs.  of  distilled  water  is  slowly  run  in 
through  the  funnel  while  the  contents  of 
the  flask  are  gently  agitated.  The  flask  is  then  heated,  cautiously  at  first, 
to  avoid  too  rapid  evolution  of  ammonia,  and  vigorously  after  a  few 
minutes.  Distillation  is  continued  until  the  volume  of  liquid  is  reduced 
by  one- third,  when  all  the  ammonia  should  have  passed  over.  At  this 
Stage  the  distillate  is  tested  with  red  litmus  paper,  and  if  no  further 
ammonia  is  being  evolved  the  conical  receiver  is  removed  and  the  excess 
of  standard  acid  in  it  determined  by  titrating  with  semi-normal  sodium 
carbonate,  using  Methyl  Orange  as  indicator. 

If  there  is  any  doubt  about  the  purity  of  the  reagents  used,  a  blank 
"experiment  should  be  performed,  using  the  same  quantities  of  the  same 
reagents  under  the  same  conditions.  The  volume  of  the  standard  acid 
neutralised  in  the  blank  experiment  is  deducted  from  the  volume  of  acid 
neutralised  in  the  determination — • 


Fig.  68. 


%  of  nitrogen 


N 

Volume  of  ^  acid  neutralised  X  0-007  X  100 
Weight  of  substance  taken. 


CHAPTER  XXXVI 


QUANTITATIVE  ESTIMATION  OF  HALOGENS  AND  SULPHUR 

Carius  Method. — The  method  of  Carius,  which  is  applicable  to  practically 
all  types  of  organic  halogen  compounds,  consists  in  oxidising  the  substance 
with  fuming  nitric  acid,  under  pressure  in  presence  of  silver  nitrate.  The 
silver  halide  formed  is  then  separated  by  filtration  and  weighed. 

The  following  are  required  for  the  analysis  : 

1.  A  tube  of  thick  walled  soft  tubing  about  50  cms.  long,  12 — 13  mms. 
inside  diameter,  and  walls  2 — 3  mms.  thick.  Tubes  of  hard  potash  glass 
with  walls  2  mms.  thick  may  also  be  used.  The  tube  is  carefully  sealed 
at  one  end,  in  the  manner  described  on  p.  38,  after  which  it  is  thoroughly 
washed  and  dried. 

2.  A  weighing  tube,  about  10  cms.  long,  sealed  at  one  end  and  of  such 
a  diameter  that  it  slips  easily  into  the  thick  walled  tube. 

3.  A  funnel  tube  or  thistle  funnel,  about  40  cms.  long,  which  fits  into 
the  sealed  tube  and  serves  to  convey  the  silver  nitrate  and  fuming  nitric 
acid  to  the  bottom  of  this  tube. 

4.  Pure  fuming  nitric  acid,  the  purity  of  which  should  be  tested  by 
diluting  2  c.cs.  of  it  with  50  c.cs.  of  distilled  water  and  adding  a  few  drops 
of  silver  nitrate  solution.  The  liquid  should  remain  perfectly  clear.  If 
it  contains  chlorine,  it  must  be  redistilled  over  a  few  crystals  of  silver 
nitrate. 

5.  A  tube  furnace  (bomb  furnace).    (See  p.  40.) 

6.  Solid  silver  nitrate. 

Filling  and  Sealing  the  Tube. — The  exact  weight  of  the  weighing  tube 
is  determined.  Into  it  is  placed  about  0-2 — 0-3  gm.  of  the  substance  to 
be  analysed,  finely  powdered,  and  the  tube  plus  its  contents  exactly 
weighed  again.  By  means  of  the  funnel  tube,  a  quantity  of  finely  pow- 
dered silver  nitrate  varying  from  0-5 — 1-0  gm. — according  to  the  per- 
centage of  halogen-- is  introduced  into  the  sealed  tube.  This  is  followed 
by  2  c.cs.  of  fuming  nitric  acid.  The  funnel  tube  is  then  removed,  care 
being  taken  not  to  touch  the  sides  of  the  sealed  tube  with  it,  and  while  the 
latter  is  held  at  a  slight  angle,  the  weighing  tube  is  allowed  to  slide  gently 
down  to  the  bottom  of  it,  but  the  substance  must  not  come  into  contact 
with  the  acid.  The  open  end  of  the  sealed  tube  is  then  sealed  in  the  blow- 
pipe, as  described  on  p.  40,  care  being  taken  that  during  the  sealing  the 
substatice  does  not  come  in  contact  with  the  acid. 

When  the  substance  to  be  analysed  is  a  liquid,  it  is  placed  in  a  bulb 
tube  with  an  open  capillary  (for  filling,  see  p.  447),  which  is  introduced, 
bulb  foremost,  into  the  tube  after  the  silver  nitrate  and  nitric  acid  have 
been  inserted. 

458 


ESTIMATION  OF  HALOGENS  AND  SULPHUR  459 


Heating  the  Tube. — When  cold,  the  tube  is  placed  in  an  iron  protecting 
cylinder,  and  the  whole  transferred  to  a  tube  furnace,  where  it  is  heated 
according  to  the  directions  given  on  p.  41.  The  temperature  and 
duration  of  heating  depend  on  the  greater  or  less  resistance  of  the  sub- 
stance towards  decomposition.  With  many  compounds  that  oxidise 
easily,  2 — 4  hours  at  150° — 200°  is  sufficient,  while  substances  which  do 
not  easily  oxidise,  especially  those  containing  sulphur,  must  be  heated 
8 — 10  hours  and  as  high  as  250° — 300°.  It  is  advisable  to  commence  the 
operation  in  the  morning,  and  to  raise  the  temperature  gradually  to  200° 
during  the  first  four  hours,  and  to  250°  or  300°  during  the  second  period  of 
4  hours.  Practically  all  substances  are  decomposed  by  this  treatment. 
For  any  particular  substance,  experiment  will  show  whether  the  duration 
of  heating  and  the  temperature  may  be  reduced. 

Opening  the  Sealed  Tube. — The  tube  is  allowed  to  remain  in  the  furnace 
until  perfectly  cold.  The  iron  protecting  case  containing  the  tube  is  then 
removed  from  the  furnace,  and  the  capillary  end  of  the  tube  allowed  to 
project  3  or  4  cms.  Before  heating  the  capillary  to  softening  in  a  large 
name,  care  must  be  taken  to  drive  back  into  the  tube,  by  gently  heating 
over  a  small  flame,  any  liquid  which  may  have  collected  in  the  capillary. 

Fall  directions  are  given  on  p.  41  for  opening  the  capillary.  After 
opening  the  capillary,  the  tube  is  removed  from  the  case,  and  examined 
to  see  if  it  still  contains  crystals  or  oily  drops  of  the  undecomposed  sub- 
stance. If  it  does,  the  capillary  is  again  sealed,  and  the  tube  reheated  in 
the  furnace  ;  but  if  it  does  not,  a  deep  file  scratch  is  made  in  the  wide  part 
of  the  tube  about  3  cms.  below  the  shoulder  of  the  capillary  and  the  end 
broken  off  according  to  the  second  method  of  opening  sealed  tubes  (p.  42). 

The  tube  is  then  held  almost  in  a  horizontal  position,  and  the  conical 
end  removed  ;  any  fragments  of  broken  glass  are  carefully  wiped  off,  and 
not  allowed  to  become  admixed  with  the  contents  of  the  tube.  The  part 
broken  off  is  washed  free  from  any  liquid  or  precipitate  which  may  have 
adhered  to  it,  with  distilled  water  into  a  beaker.  The  contents  of  the  tube 
are  diluted  with  distilled  water  and  poured  into  the  beaker,  care  being 

% taken  that  the  fall  of  the  weighing  tube  does  not  injure  the  beaker.  The 
tube  is  held  in  an  inverted  position  over  the  beaker,  and  the  outer 

■  edges  of  the  open  end  washed  with  distilled  water.  The  precipitate  still 
remaining  in  the  tube  is  washed  out  by  repeated  shakings  with  small 
quantities  of  distilled  water,  any  precipitate  which  is  attached  to  the  tube 
may  be  loosened  by  rubbing  with  a  long  piece  of  glass  rod,  over  the  end  of 
which  is  placed  a  short  piece  of  rubber  tubing.*  The  short  end  of  a  thin 
piece  of  glass  rod  bent  at  a  right  angle  is  then  inserted  in  the  mouth  of  the 
weighing  tube,  and  while  the  latter  is  removed  just  above  the  surface  of 
the  liquid,  the  outside  is  washed  with  distilled  water.  It  is  then  held  in 
the  fingers  and  the  inside  washed  with  distilled  water  into  the  beaker. 

Estimation  oi  the  Silver  Halide. — The  contents  of  the  beaker  are  now 
heated  to  boiling,  until  the  silver  halide  settles  and  the  supernatant  liquid 

*  The  last  traces  of  silver  halide  may  be  removed  from  the  tube  by 
washing  out  with  ammonia  into  the  beaker.  Extra  nitric  acid  must  in  this 
case  be  added  to  the  contents  of  beaker. 


460  SYSTEMATIC  ORGANIC  CHEMISTRY 


is  clear.  Any  lumps  amongst  the  precipitate  are  crushed  from  time  to 
time  to  ensure  that  the  silver  nitrate  is  completely  dissolved  out.  A 
Gooch  crucible,  fitted  with  a  paper  disc,  is  prepared  ;  a  quantity  of  dilute 
nitric  acid,  approximately  the  same  in  volume  and  concentration  as  that 
in  the  beaker,  is  filtered  through  it.  It  is  then  washed  well  with  distilled 
water  and  dried  in  an  air  oven  at  140° — 150°,  after  which  it  is  weighed. 
The  contents  of  the  beaker  are  then  filtered  with  suction  through  the 
crucible,  washed  free  from  silver  nitrate  with  distilled  water,  and  finally 
dried,  until  constant  in  weight,  at  140° — 150°  in  an  air  bath  (30  minutes). 
The  weight  of  silver  halide  is  then  determined. 

°/  of  halo  en  —        X  °^  na^°Sen  x       of  Ag  halide 

/o  o   la  ogen  —  wt#  0f  SUDstance  taken  X  M.  W.  of  Ag  halide 

A  method — somewhat  more  liable  to  error — of  estimating  the  silver  halide 
consists  in  filtering  the  contents  of  the  beaker  through  the  usual  paper 
and  funnel,  washing  the  precipitate  thoroughly  with  distilled  water,  and 
drying  in  the  steam  oven.  The  paper  and  precipitate  are  then  incinerated 
in  the  usual  way. 

Notes.—- It  sometimes  happens  that,  even  after  taking  the  precautions 
advised,  the  silver  halide  is  mixed  with  fragments  of  glass.  If  this  happens 
in  the  case  of  silver  chloride,  the  precipitate  after  filtering  and  washing 
should  be  digested  in  the  Gooch  with  warm  dilute  ammonia  solution, 
which  dissolves  out  the  silver  chloride.  Any  fragments  of  glass  are  then 
filtered  off,  and  the  pure  silver  chloride  in  the  filtrate  precipitated  by 
acidifying  with  hydrochloric  acid.*  When  fragments  of  glass  are  mixed 
with  silver  iodide,  the  separation  is  much  more  difficult.  The  silver 
iodide  plus  glass  is  first  estimated,  and  afterwards  left  in  contact  with 
dilute  sulphuric  acid  and  a  piece  of  chemically  pure  zinc ;  after  several 
hours  the  silver  halide  is  reduced  to  metallic  silver.  The  supernatant 
liquors  are  decanted  from  the  silver  and  glass,  which  are  washed  several 
times  by  decantation  with  water.  The  silver  is  dissolved  in  dilute  nitric 
acid  and  the  fragments  of  glass  collected  on  a  filter,  dried  and  weighed. 

The  only  chlorine  and  bromine  compounds  which  fail  to  give  good  results 
by  this  method  are  the  highly  halogenated  aromatic  derivatives,  such  as 
hexachlorobenzene.  Iodine  compounds  often  give  unreliable  results, 
since  silver  iodide  is  appreciably  soluble  in  a  nitric  acid  solution  of  silver 
nitrate.  Free  iodine  is  also  formed  in  some  instances  (see  note  on  next 
method). 

Method  of  Pira  and  Schiff. — This  method  is  only  applicable  to  those 
organic  substances  which  are  not  highly  volatile.  Liquids  which  combine 
directly  with  lime  or  sodium  carbonate  may  also  be  analysed  in  this  way. 

About  04 — 0-3  gm.  of  the  substance  is  weighed  into  a  very  small 
platinum  crucible,  which  is  then  filled  up  with  an  intimate  mixture  of 
sodium  carbonate  (1  part)  and  pure  powdered  quicklime  (4 — 5  parts). 
The  crucible  is  then  placed  in  an  inverted  position  in  a  larger  platinum 
crucible,  the  space  between  the  two  being  completely  filled  with  the 

*  Silver  bromide,  though  much  less  soluble  in  ammonia  than  silver  chloride, 
may  also  be  freed  from  glass  in  this  manner. 


ESTIMATION  OF  HALOGENS  AND  SULPHUR  461 


same  mixture  of  sodium  carbonate  and  lime,  so  that  the  small  crucible  is 
entirely  covered. 

The  large  crucible  is  now  heated  in  a  large  Bunsen  or  blowpipe  flame,  so 
that  the  outer  portions  attain  a  high  temperature  before  the  substance  in 
the  smaller  crucible  begins  to  decompose.  The  whole  is  finally  raised  to  a 
red  heat.  The  crucibles  and  contents  are  allowed  to  cool,  then  digested 
with  water  in  a  strong  beaker.  Dilute  nitric  acid  is  cautiously  added 
until  the  solution  reacts  acidic,  care  being  taken  that  the  temperature  does 
not  rise  to  any  extent.  External  cooling  is  advisable.  The  solution  is 
filtered  to  remove  any  carbonaceous  matter,  and  the  halogen  precipitated 
with  silver  nitrate  and  estimated  as  described  in  the  Carius  method. 

When  the  substance  contains  iodine,  the  method  requires  modification  ; 
sodium  carbonate  is  then  employed  alone,  as  calcium  iodate  would  be 
formed  were  lime  present.    If  any  iodine  appears  after  acidification  with 
nitric  acid,  it  is  reduced 
to  hydriodic  acid  with  the 
minimum  quantity  of  sul- 
phurous acid.  r\  =x 

Bromine  and  Chlorine  =  J  | 
(Robertson).  —  The  prin-  J 

ciple     underlying     the  f  \  .  , 

method  is  that  organic 
substances  containing 
these  elements  give  them 
up  entirely  in  a  volatile 
form  when  heated  with  a 
mixture  of  chromic  and 
sulphuric  acids  ;  bromine 
compounds  yield  a  mix- 
ture of  bromine  and 
hydrogen  bromide,  which 
is  absorbed  in  alkaline  FIG>  69. 

hydrogen    peroxide  as 

alkali  bromide.  Chlorine  compounds  yield  chlorine,  hydrogen  chloride 
and  chromyl  chloride ;  these  are  absorbed  in  alkaline  hydrogen 
peroxide  with  the  formation  of  alkali  chloride  and  chromates  ;  and 
after  reduction  of  the  chromate,  which  would  mask  the  end  point,  the 
chlorine  in  the  solution  is  estimated  in  the  usual  way  with  silver  nitrate 
and  thiocyanate. 

The  Apparatus  (Fig.  69). — The  reaction  vessel,  a  flask  of  about  70  c.cs. 
capacity,  fitted  with  a  ground-glass  joint,  to  which  are  attached  an  inlet 
and  an  exit  tube,  is  heated  by  radiation  from  an  asbestos  gauze  placed 
2-5  cms.  beneath  it.  The  absorption  apparatus  consists  of  a  bulb  tube 
fitted  to  the  exit  tube  of  the  reaction  flask  by  a  ground-glass  connection, 
and  a  second  smaller  U-tube  which  serves  as  a  guard. 

The  reagents  required  are  pure  redistilled  sulphuric  acid,  chromic  acid, 
10%  sodium  hydroxide  solution,  and  hydrogen  peroxide  solution  free  from 
chloride. 


462 


SYSTEMATIC  ORGANIC  CHEMISTRY 


The  Method. — Enough  of  the  substance  to  give  halogen  equivalent  to 

about  9  c.cs.  of  ^  silver  nitrate  is  weighed  from  a  small  tube  (or,  if  a  liquid, 

either  from  a  Sprengel  pipette  or  in  a  bulb  tube)  into  the  reaction  vessel. 
4 — 6  gms.  of  chromic  acid  are  then  introduced.  The  ground-glass 
joint,  lubricated  with  syrupy  phosphoric  acid,  is  fixed  in  position,  and  the 
flask  is  connected  to  the  absorption  apparatus.  To  the  large  U-tube  are 
added  10  c.cs.  of  the  sodium  hydroxide  solution,  and  the  same  volume  of 
hydrogen  peroxide  solution  (or  water  and  1 — 2  c.cs.  of  perhydrol).  The 
smaller  U-tube  contains  a  little  sodium  hydroxide  solution.  Then  by 
means  of  a  small  funnel  or  pipette,  25 — 30  c.cs.  of  sulphuric  acid  are 
poured  down  the  inlet  tube  into  the  reaction  vessel,  and  a  slow  current  of 
dry  air  is  blown  or  aspirated  through  the  apparatus. 

In  many  cases  the  decomposition  begins  at  once,  and  should  be 
moderated  by  external  cooling  in  case  it  tends  to  become  violent.  In 
other  cases  heating  should  be  commenced  with  a  small  flame,  but  the 
source  of  heat  should  be  immediately  removed  if  the  evolution  of  gas 
becomes  too  vigorous.  After  about  10  minutes,  the  initial  vigour  of  the 
reaction  will  have  subsided,  and  the  heating  may  be  increased,  and  the 
stream  of  air  made  more  rapid.  When  adjusted  at  this  stage,  the  appa- 
ratus may  be  left  without  further  attention,  and  in  45 — 60  minutes  the 
colour  of  bromine  or  chromyl  chloride  will  have  disappeared  from  the 
reaction  vessel,  and  the  operation  will  be  complete.  It  is  advisable  to 
shake  round  the  contents  of  the  flask  towards  the  end  of  the  experiment, 
as  sometimes  particles  of  partly  decomposed  substance  are  projected  above 
the  level  of  the  sulphuric  acid. 

The  contents  of  the  absorption  tubes  are  now  washed  into  a  conical 
flask.    In  the  case  of  a  bromine  estimation,  the  solution  is  acidified  with 

N 

nitric  acid,  and  10  c.cs.  of  —  silver  nitrate  are  added  from  a  pipette  ;  the 

contents  of  the  flask,  cooled  if  necessary,  are  now  titrated  with  thiocyanate 

in  the  usual  manner.    If  chlorine  is  being  estimated,  it  is  necessary  to 

destroy  the  highly  coloured  chromate,  which  would  obscure  the  end  point. 

For  this  purpose,  the  liquid  is  heated  to  boiling,  and  then  neutralised  with 

nitric  acid.    In  the  presence  of  hydrogen  peroxide,  the  chromate  is  reduced 

to  a  chromic  salt,  which  at  the  dilution  of  the  experiment,  is  practically 

colourless.    10  c.cs.  of  standard  silver  nitrate  are  added,  the  solution  is 

filtered  free  from  silver  chloride  (which  reacts  with  thiocyanate),  cooled, 

and  the  excess  of  silver  in  the  filtrate  estimated. 

Standardisation  of  Reagents. — In  order  to  obtain  accurate  results,  it  is 

necessary  to  standardise  the  silver  nitrate  and  thiocyanate  solutions  with 

pure  potassium  bromide  under  exactly  the  same  conditions  as  those  of  the 

experiment.    For  this  purpose  potassium  bromide  equivalent  to  about 

N    .         .  . 
9  c.cs.  of        silver  nitrate  is  dissolved  in  a  little  water,  and  sodium 

hydroxide  and  hydrogen  peroxide  are  added  to  the  solution  ;  after 
acidification  with  nitric  acid,  10  c.cs.  of  the  silver  nitrate  solution  are: 


ESTIMATION  OF  HALOGENS  AND  SULPHUR 


463 


N 

added,  and  the  excess  of  silver  is  titrated  with  ^— ^  thiocyanate.    By  this 

method  any  errors  caused  by  the  presence  of  traces  of  chloride  in  the 
reagents  or  due  to  the  very  slight  influence  of  hydrogen  peroxide  are  all 
eliminated.  It  should  be  noticed  that  in  presence  of  hydrogen  peroxide, 
the  red  colour  of  ferric  thiocyanate  disappears  in  the  course  of  several 
minutes. 

Except  in  the  case  of  a  few  bromohydrocarbons  the  method  gives 
excellent  results.  It  is  advisable  to  carry  out  a  blank  determination 
under  exactly  the  same  conditions  as  an  actual  determination.  For  a 
discussion  of  results,  see  original  paper  (J.  C.  S.  107,  902.) 

Quantitative  Estimation  of  Sulphur 

Method  of  Carius. — The  process  is  almost  the  same  as  that  described 
under  the  estimation  of  halogens.  The  compound  is  oxidised  in  a  sealed 
tube  with  fuming  nitric  acid,  but  neither  silver  nitrate  nor  barium  chloride 
are  placed  in  the  tube.  The  resulting  sulphuric  acid  is  precipitated  and 
weighed  as  barium  sulphate.  Similar  quantities  of  substance  and  of 
fuming  nitric  acid  are  taken,  and  the  processes  of  sealing,  heating  and 
opening  the  tube  are  conducted  in  the  same  way  as  for  halogens.  The 
contents  of  the  tube,  after  being  washed  out  into  a  beaker,  are  filtered  free 
from  fragments  of  glass.  The  filtrate  is  diluted  to  about  300  c.cs.  with 
water,  heated  to  boiling,  and  the  sulphuric  acid  precipitated  as  barium 
sulphate  by  the  addition  of  barium  chloride  solution.  A  large  excess  of 
barium  chloride  should  not  be  added  owing  to  the  sparing  solubility  of 
barium  nitrate  in  aqueous  mineral  acids  ;  this  can  be  avoided  by  allowing 
the  precipitate  to  settle  before  adding  more  of  the  solution.  The  liquid  is 
heated  over  a  small  flame  until  (sometimes  1 — 2  hours)  the  precipitate 
settles  and  the  supernatant  liquid  is  clear.  It  is  then  filtered  either 
through  an  ordinary  funnel,  or  through  a  Gooch  crucible  (see  Halogen 
Estimation),  and  the  precipitate  washed  well  with  hot  water.  The  weight 
of  barium  sulphate  is  finally  determined. 

°/  of  sul  hur  -    Wt'  °f  BaS°4  x  32  x  100 
^  233  X  wt.  of  substance  taken 

Frequently  in  this  method  a  considerable  amount  of  gas  is  evolved,  and 
the  tube  is  liable  to  burst.  In  such  cases  the  sealed  tube  should  be  heated 
only  to  200°  for  2  hours,  after  which  it  is  allowed  to  cool,  and  the  capillary 
opened  to  allow  the  gases  to  escape.    It  is  then  resealed  and  heated  to  300°. 

Many  sulphur  compounds,  especially  aliphatic  sulphides,  do  not  give 
accurate  results,  as  the  sulphones  formed  by  the  action  of  nitric  acid  are 
generally  so  stable  as  to  resist  further  decomposition  by  the  acid.  When 
stable  sulphones  are  formed,  the  contents  should  be  washed  out  into  a 
nickel  basin,  made  alkaline  with  caustic  potash,  and  evaporated  to  dry- 
ness. The  residue  is  then  treated  as  described  in  the  Estimation  of  Sul- 
phur by  Fusion. 

Fusion  Method. — This  method  is  applicable  only  to  substances  which 


464  SYSTEMATIC  ORGANIC  CHEMISTRY 


are  not  easily  volatile.  A  quantity  of  the  substance — 0-2  to  0-4  gm. — is 
intimately  mixed  with  4  gms.  sodium  peroxide  and  7  gms.  sodium  carbonate 
in  an  iron  crucible.*  It  is  heated  very  cautiously  with  a  small  flame 
which  does  not  touch  the  crucible  at  first.  The  flame  is  very  gradually 
increased  until  the  crucible  is  ultimately  raised  to  a  red  heat,  at  which  it 
is  maintained  for  half  an  hour.  (Note. — Great  care  is  necessary  in  the 
early  stages  of  the  heating,  in  order  to  avoid  explosive  reaction.) 

The  melt  is  allowed  to  cool,  taking  care  to  avoid  loss  of  any  material 
which  may  have  crept  up  the  sides  of  the  crucible.  It  is  then  digested 
with  water,  a  few  c.cs.  of  bromine  water  added,  and  the  resulting 
solution  with  the  crucible  and  lid  in  it  warmed  on  the  water  bath  for  half 
an  hour.  The  crucible  and  lid  are  then  removed,  washed  thoroughly,  and 
the  solution  acidified  with  hydrochloric  acid  and  filtered.  The  sulphur  in 
the  filtrate  is  finally  precipitated  and  estimated  as  barium  sulphate. 

Simultaneous  Determination  of  Halogens  and  Sulphur. — The  operation  1 
is  conducted  as  described  under  the  Estimation  of  Halogens  (Carius). 
The  sealed  tube  is  charged  with  silver  nitrate,  fuming  nitric  acid  and  sub- 
stance. After  the  heating,  the  silver  halide  is  filtered  off  and  estimated. 
The  filtrate,  which  contains  the  excess  of  silver  nitrate  in  addition  to  the 
sulphuric  acid  formed  by  oxidation,  is  warmed,  and  to  it  is  added  a  boiling 
solution  of  barium  nitrate  (free  from  chloride).  The  solution  should  be 
very  dilute — about  500  c.cs.  for  0-3 — 0-4  gms.  substance  originally  taken — 
and  an  excess  of  barium  nitrate,  owing  to  its  sparing  solubility,  is  to  be 
avoided.  The  barium  sulphate  is  estimated  as  described  under  Deter- 
mination of  Sulphur. 

*  The  reagents  used  must  be  pure. 


OHAPTEE  XXXVII 


MOLECULAR  WEIGHT  DETERMINATION 


The  methods  mostly  employed  in  organic  chemistry  for  the  deter- 
mination of  molecular  weights  are  the  vapour  density  method  of  Victor 
Meyer  and  the  freezing  point  method  of  Raoult ;  the  former  being  simple 
and  rapid  in  practice  is  almost  universally  employed  where  possible.  The 
boiling  point  method  is  sometimes  employed. 

Method  of  Victor  Meyer. — This  method,  which  is  used  for  substances 
which  volatilise  without 
decomposition,  involves 
the  use  of  the  apparatus 
shown  in  Fig.  70.  The 
inner  vessel  A  consists  of 
an  elongated  glass  bulb 
with  a  long  narrow  stem  ; 
it  is  carked  at  the  top,  near 
to  which  point  a  side  tube, 
which  serves  to  deliver  gas 
into  a  measuring  tube  C 
full  of  water  and  standing 
in  a  trough  of  water,  is 
sealed.  Before  commenc- 
ing the  operation,  A  is 
thoroughly  cleaned  and 
dried,  and  a  small  quantity 
of  previously  ignited  sand 
or  asbestos — to  break  the 
fall  of  the  Hoffmann  bottle 
when  it  is  dropped  in — is 
placed  at  the  bottom  of 
the  bulb.  The  bulb  of  the 
outer  jacket  B  is  half  filled 
with  a  liquid  whose  boiling 
point  is  20° — 30°  above  that  of  the  substance  whose  molecular  weight  is 
to  be  determined  ;  a  few  pieces  of  broken  porcelain  are  also  added  to 
induce  regular  boiling.  B  may  be  of  glass,  copper  or  tinplate,  the  last  two 
being  more  durable.  The  inner  vessel  is  fixed  in  the  outer  by  means  of 
a  split  cork  which  has  been  suitably  bored  (before  splitting)  to  accommo- 
date the  neck  of  A,  and  a  bent  glass  tube  which  conveys  away  the  vapours 
of  the  boiling  liquid. 

While  the  liquid  in  B  is  being  heated  to  boiling,  about  0-1  gm.  of  the 

s.o.c.  465  h  h 


Fig.  70. 


466  SYSTEMATIC  ORGANIC  CHEMISTRY 


substance  to  be  determined  is  weighed  out  in  the  Hoffmann  bottle  H. 
As  the  air  in  A  expands  on  heating  (A  being  corked)  it  is  allowed  to  escape 
through  the  capillary  tube  without  entering  the  measuring  tube.  But  as 
soon  as  a  constant  temperature  is  reached,  no  further  expansion  of  the  air 
in  A  takes  place,  as  indicated  by  no  further  escape  of  bubbles  from  the 
capillary.  (It  is  important  to  protect  the  burner  and  the  apparatus  from 
draughts.)  When  this  point  is  reached,  the  graduated  measuring  vessel 
is  placed  over  the  end  of  the  delivery  tube,  and  the  cork  in  A  is  momen- 
tarily withdrawn  while  the  loosely-corked  Hoffmann  bottle  is  dropped  in. 
The  substance  is  quickly  converted  into  vapour,  which  expels  its  own 
volume  of  air  into  the  measuring  vessel.  In  the  course  of  a  minute  or  two, 
when  no  more  bubbles  pass  into  the  measuring  cylinder,  it  is  transferred 
while  closed  by  the  thumb  to  a  deep  cylinder  filled  with  water.  It  is  left 
for  15  minutes  prior  to  adjusting  the  internal  and  external  liquids  to  the 
same  level,  when  the  volume  V  of  air  is  read  off.  The  temperature  t, 
indicated  by  a  thermometer  immersed  in  the  deep  cylinder,  and  the 
barometric  pressure  P  are  at  the  same  time  noted.  Then  if  W  =  weight 
of  substance  employed,  and  p  ==  vapour  tension  of  water  at  the  tem- 
perature t} 


Freezing  Point  Method  oi  Raoult. — The  depression  of  the  freezing 
point  of  a  solvent,  caused  by  the  presence  of  a  liquid  or  solid  in  solution, 
is  directly  proportional  to  the  amount  of  substance  dissolved,  and  inversely 
proportional  to  its  molecular  weight.  Thus  if  d  =  depression  of  the 
freezing  point,  w  —  weight  of  substance  of  molecular  weight  M,  dissolved 
in  100  gms.  of  solvent,  and  k  =  a  constant  called  the  molecular  depression, 
which  is  constant  for  each  solvent  and  which  may  either  be  determined 
or  obtained  from  tables,  then 


This  rule  does  not  apply,  however,  to  substances  which  dissociate  in 
certain  solvents,  nor  to  substances  which  form  molecular  aggregates  in 
solution.  Thus,  strong  electrolytes  should  not  be  determined  in  aqueous 
solution,  nor  should  the  solvent  be  such  that  mixed  crystals  of  solvent 
and  solute  separate. 

The  values  of  k  for  the  following  solvents  are  : — 


the  molecular  weight  = 


W  X  22,400  X  760  (273  +  t) 
V(P-p)  X273 


gms. 


d  =  k^f.    And  hence  M  =  k-j. 


Water 
Benzene 


Acetic  acid  . 
Nitrobenzene 
Phenol 


Naphthalene 


M.P. 

0° 

5-5° 
17° 

5-3° 
40° 
79-6° 


k 

18-5 

50 

39 

69 

72 

69 


MOLECULAR  WEIGHT  DETERMINATION  467 


The  Apparatus. — The  diagram,  Fig.  71,  shows  the  form  of  apparatus 
generally  used  for  the  determination.  The  freezing  point  tube  (inner 
tube)  has  a  side  tube  through  which  the  solute  is  introduced,  and  is  fitted 
with  a  rubber  stopper  A  perforated  with  two  holes.  Through  one  of  these  a 
piece  of  glass  tube  passes,  in  which  a  platinum  stirrer  moves  up  and  down. 
Through  the  other  the  stem  of  a  Beckmann  thermometer  passes.  The 


£2 


Fig.  71. 


freezing  point  tube  is  fitted  by  means  of  a  rubber  stopper  into  a  larger  tube 
which  serves  as  an  air  bath  and  prevents  the  freezing  point  tube  from 
coming  into  contact  with  the  freezing  mixture  contained  in  the  large  glass 
bath.    A  syphon  B,  for  emptying  the  cooling  bath,  is  shown. 

Beckmann  Thermometer :  —  This  specially  constructed  thermometer 
has  only  a  range  of  6°,  which  are  divided  into  hundredths.  The  amount 
of  mercury  in  the  bulb  and  stem  can  be  varied  by  transferring  some  to  the 
reservoir  at  the  top  or  by  adding  some  from  the  reservoir,  and  hence  it  is 
possible  to  adjust  the  thermometer  so  as  to  get  a  scale  reading  at  a  desired 

H  H  2 


468 


SYSTEMATIC  ORGANIC  CHEMISTRY 


temperature.  The  numbers  on  the  scale  do  not,  therefore,  represent 
Centigrade  temperatures,  but  are  merely  relative  temperatures,  the  freezing 
point  of  the  solvent  and  that  of  the  solvent  plus  solute  being  determined 
on  the  same  adjustment  of  the  thermometer. 

Adjustment  of  the  Bechnann  Thermometer. — If  it  is  desired  to  work  with 
a  solvent  whose  freezing  point  is  t°,  it  is  necessary  that  the  amount  of 
mercury  in  the  bulb  is  such  that  when  the  temperature  is  f  or  1° — 2° 
lower,  the  top  of  the  mercury  thread  can  be  read  off  on  the  scale.  The 
value  of  the  mercury  thread  in  degrees  between  the  top  of  the  scale  and 
the  orifice  of  the  reservoir  is  first  determined  by  warming  the  bulb  side  by 
side  with  an  ordinary  thermometer  in  a  stirred  water  bath  until  a  little 
bead  of  mercury  issues  into  the  orifice  ;  the  burner  is  withdrawn,  the  head 
of  the  Beckmann  thermometer  is  given  a  slight  tap  to  cause  the  bead  of 
mercury  to  fall  from  the  orifice  into  the  reservoir,  and  the  temperature  on 
the  ordinary  thermometer  noted.  The  bath  is  allowed  to  cool,  and  the 
Centigrade  temperature  again  read  when  the  mercury  in  the  Beckmann 
thermometer  has  fallen  to  the  top  of  the  scale.  Suppose  the  value  of  the 
thread  between  scale  and  orifice  of  reservoir  to  be  equivalent  to  x°,  then 
an  amount  of  mercury  in  the  bulb  which  will  just  fill  the  thread  up  to  the 
orifice  at  t  +  x°  would  give  a  reading  of  6  (the  top  of  the  scale)  at  f.  If 
there  is  too  little  mercury  in  the  bulb  to  reach  to  the  orifice  at  t  + 
some  more  is  added  from  the  reservoir  in  the  following  way.  The  bulb  of 
the  thermometer  is  immersed  in  a  bath  or  held  in  the  hand,  and  warmed 
until  the  mercury  reaches  from  bulb  to  reservoir  ;  the  thermometer  is  then 
inverted  and  some  mercury  from  the  reservoir  caused  to  unite  with  that 
of  the  thread  at  the  orifice ;  the  temperature  is  then  allowed  to  fall  and 
when  it  reaches  t  -j-  x°  the  thermometer  is  returned  to  its  original  vertical 
position,  and  the  excess  of  mercury  at  the  orifice  caused  to  fall  into  the 
reservoir  by  gently  tapping.  At  t°  the  top  of  the  mercury  thread  should 
be  on  the  scale  and,  if  so,  the  thermometer  is  ready  for  use.  In  a  similar 
manner  an  excess  of  mercury  in  the  bulb  can  be  transferred  by  warming 
to  t  +  ^°  and  removing  at  that  temperature  the  excess  of  mercury  at  the 
orifice  by  gently  tapping. 

Determination. — The  inner  tube  is  cleaned  and  dried,  then  fitted  with 
corks  and  weighed.  Sufficient  solvent  (generally  15 — 20  c.cs.)  is  intro- 
duced to  cover  the  bulb  of  the  Beckmann  thermometer  when  it  is  immersed 
nearly  to  the  bottom  of  the  tube.  The  tube  is  again  corked  and  weighed. 
A  suitable  freezing  mixture  is  introduced  into  the  outer  cooling  bath,  the 
temperature  of  which  should  not  be  more  than  3°  below  the  freezing  point 
of  the  solution.  The  apparatus  is  assembled  as  shown  in  sketch  (Fig.  71), 
and  the  solvent  allowed  to  cool  well  below  its  freezing  point  without  stirring. 
The  solution  is  then  stirred  for  a  moment,  and  as  soon  as  crystals  begin  to 
separate,  it  is  noticed  that  the  mercury  thread  in  the  thermometer  rises. 
Continuous  and  moderately  rapid  stirring  is  employed,  and  the  maximum 
temperature  indicated  by  the  thermometer  read  off.  This  gives  an  approxi- 
mate determination  of  the  freezing  point,  and  serves  as  a  guide  in  the 
repeat  determinations.  The  inner  tube  is  removed  and  the  crystals 
melted  by  the  heat  of  the  hand  or  water  bath,  after  which  it  is  replaced  in 


MOLECULAR  WEIGHT  DETERMINATION 


469 


the  apparatus  and  the  freezing  point  again  determined — cooling  this  time 
not  more  than  0-5°  below  the  freezing  point,  before  stirring.  Two  or  three 
determinations,  which  should  agree  to  within  0-01°,  are  made  in  this 
manner,  and  the  average  taken  as  the  freezing  point  of  the  solvent.  If  the 
substance  whose  molecular  weight  is  to  be  determined  is  a  solid,  it  is 
convenient  to  fuse  it.  or  to  press  it  into  pellets  by  means  of  a  small  bullet 
mould.  A  lump  or  a  pellet,  0-1 — 0-2  gm.,  is  weighed  out,  and  introduced 
into  the  inner  tube,  which  is  removed  from  the  bath  while  the  substance 
dissolves.  The  freezing  point  of  the  solution  is  then  determined,  and  the 
operation  repeated  a  few  times — as  in  the  case  of  the  pure  solvent.  The 
difference  between  the  freezing  point  of  the  solution  and  that  of  the  pure 
solvent  is  the  depression  of  the  freezing  point. 
Example. — Naphthalene  in  benzene  : 

Weight  of  benzene         ==  20  gms. 

,,      naphthalene  =  0-195  gm. 

Depression  of  freezing  point  =  0-78° 

tvt  t     i         -  n   *       -l  .  t  i           100  X  50  X  0-195 
.".  Molecular  weight  or  naphthalene  =  Q  78  x  10  = 

Boiling  Point  Method. — The  boiling  point  of  a  pure  solvent  is  raised 
by  the  addition  of  a  solute,  the  amount  of  such  increase  being  proportional 
to  the  amount  of  solute  added.  Molecular  proportions  of  different  solutes 
produce  the  same  increase  in  boiling  point  for  a  particular  solvent ;  this 
increase  is  known  as  the  molecular  increase  for  the  solvent.  If  e°  is  the 
observed  increase  in  boiling  point  and  w  the  weight  of  substance  dissolved 
in  W  gms.  of  solvent,  and  K  the  constant  for  the  particular  solvent,  then 
the  molecular  weight  of  the  substance 

M  =  K 


e.  W 

The  following  table  gives  the  value  of  K  for  the  more  common  solvents. 
Solvent.  B.P.°  K. 


Water 

Ethyl  alcohol 
Ether 
Acetone 
Benzene 


100-0  520 

78-3  1,150 

34-9  2,100 

56-3  1,700 

80-3  2,700 


The  apparatus,  Fig.  72,  consists  of  a  boiling  tube  with  arms  on  opposite 
sides.  The  one  arm,  A,  acts  as  an  addition  tube  while  the  other,  B,  acts  as 
a  reflux  condenser  for  the  solvent,  which  is  placed  in  the  boiling  tube  C. 
The  small  outlet  tube  D  is  provided  to  allow  access  to  the  atmosphere. 
A  Beckmann  thermometer  E  is  inserted  through  a  cork  in  the  neck  of  C. 
The  bulb  of  the  tube  C  is  surrounded  by  an  air  jacket  F  and  by  a  further 
air  jacket  G,  which  are  simply  hollow  cylinders,  sitting  on  an  asbestos 
plate  II  and  covered  with  a  mica  plate  K.    By  this  means  heating  is 


470  SYSTEMATIC  ORGANIC  CHEMISTRY 


made  more  uniform,  and  the  tube  is  protected  against  loss  of  heat  by 
radiation. 

The  Beckmann  thermometer  is  first  set  (see  p.  467),  so  that  the  boiling 
point  of  the  solvent  to  be  used  is  registered  near  the  middle  of  the  scale. 
A  weighed  quantity  of  the  solvent,  15—20  gms.,  is  quickly  introduced  into 
the  boiling  tube,  and  a  few  glass  beads  or  similar  material  are  also  added 
to  induce  regular  boiling.  The  thermometer  is  then  quickly  inserted,  so 
that  its  bulb  is  just  above  the  beads  and  entirely  surrounded  by  liquid. 
The  condenser  is  also  quickly  placed  in  position,  and  heating  is  com- 


menced. The  Bunsen  should  be  regulated  so  that  the  liquid  boils  vigor- 
ously, and  the  same  rate  of  ebullition  should  be  maintained  throughout 
the  experiment.  The  boiling  point  of  the  pure  solvent  is  noted,  and  the 
final  reading  of  the  thermometer  should  not  be  taken  until  the  mercury 
has  remained  stationary,  which  usually  requires  about  half  an  hour,  the 
thermometer  being  slightly  tapped  before  taking  any  reading. 

When  the  substance  of  which  the  molecular  weight  is  to  be  determined 
is  a  solid,  a  number  of  tabloids,  each  about  0-2  gm.,  are  made  with  a  press. 
The  first  piece  is  carefully  weighed  and  introduced  through  the  addition 
tube.    The  temperature  is  again  noted  when  it  has  become  constant  for 


MOLECULAR  WEIGHT  DETERMINATION  471 


5  minutes  ;  a  second  piece  is  introduced  and  again  the  temperature 
read,  and  so  on,  and  the  molecular  weight  is  calculated  for  each  con- 
centration. 

0-2  gm.  should  be  subtracted  from  the  weight  of  solvent  when  this  is 
ether,  acetone,  alcohol  or  benzene,  and  0-35  gm.  when  the  solvent  is  water, 
to  allow  for  the  quantity  of  solvent  clinging  to  the  condenser,  etc. 

When  the  substance  is  liquid,  it  is  introduced  into  the  boiling  tube  by 
means  of  a  pyknometer  with  a  long  side  tube,  which  discharges  the  liquid 
so  that  it  falls  direct  into  the  solvent. 

Since  the  boiling  point  is  a  function  of  the  pressure,  the  barometer  should 
be  read  both  at  the  beginning  and  at  the  end  of  the  experiment,  and  a 
correction  made  if  necessary. 

Example. — Anthracene  in  benzene. 


Observed  increase 
Weight  of  solvent 
,,  anthracene 


K  =  2,700 
=  0-180° 

=  17-7  -  0-2  =  17-5  gms, 
e  —   0-21  gm. 


.-.  M  - 


CHAPTER  XXXVIII 


Determination  of  the  Equivalent  of  an  Acid. 


N 


By  Titration  with  Standard  Alkali. —  —  aqueous  and  alcoholic  potash 
N  . 

as  well  as  ^  baryta  solution  are  used  for  titrating  organic  acids,  phenol- 

phthalein  being  in  all  cases  the  best  indicator.    Baryta  solution  is  the 

most  suitable  alkali  since  it 
can  be  prepared  and  kept 
free  from  carbonate.  The 
baryta  solution  is  contained 
in  the  apparatus.  Fig.  73. 
The  storage  bottle  is  con- 
nected to  the  top  and 
bottom  of  a  burette  having 
a  2-way  stopcock,  and  the 
baryta  solution  is  protected 
from  atmospheric  carbon 
dioxide  by  a  soda-lime  tube 
inserted  through  the  cork 
in  the  top  of  the  storage 
bottle. 

The  baryta  solution  is 
prepared  from  pure  crystal- 
line barium  hydroxide, 
Ba(OH)2.8H20,  by  dissolv- 
ing in  distilled  water.  Any 
carbonate  is  allowed  to  sub- 
side and  the  clear  super- 
natant liquid  syphoned  into 
the  storage  bottle  after  the 
latter  has  been  filled  with 
air  free  from  carbon  dioxide. 

To  determine  the  equiva- 
lent of  an  acid,  a  suitable 
quantity  of  it — determined 
by  trial  titrations — is  dis- 
solved in  distilled  water  if 
soluble  in  water,  and  if 
insoluble  in  water  in  aqueous  alcohol,  or  in  alcohol  free  from  acid.  The 


average  of  a  few  re* 


lings  which  should  agree 
472 


to  within  0-5%  is  taken, 


DETERMINATION  OF  EQUIVALENT  OF  AN  ACID  473 


and  the  amount  of  acid  necessary  to  neutralise  85-5  gms.  of  barium 
hydroxide  calculated. 

Preparation  and  Analysis  of  a  Silver  Salt. — The  preparation  and 
analysis  of  metallic  salts  is  the  chief  method,  of  determining  the 
equivalent  of  an  organic  acid.  Salts  of  silver,  calcium,  barium,  sodium 
or  potassium  may  be  used,  and  a  few  preliminary  tests  will  reveal  which 
salt  is  the  most  suitable.  Generally  the  silver  salt,  when  sparingly 
soluble  in  water,  is  selected,  since  its  isolation,  purification,  and  decom- 
position can  be  readily  effected.  Silver  salts  of  organic  acids  usually 
crystallise  without  water  of  crystallisation,  but  some  have  the  dis- 
advantage of  being  easily  attacked  by  light. 

A  small  quantity  of  the  acid  is  neutralised  with  pure  aqueous  ammonia, 
and  the  excess  of  the  latter  boiled  off.  Sufficient  silver  nitrate  is  then 
added  and  the  liquid  cooled.  Crystals  of  the  sparingly  soluble  silver 
salt  separate  and  are  filtered  off.  These  are  recrystallised  when  possible 
from  hot  water,  collected,  well  washed,  dried  in  a  steam  oven  for 
30  minutes,  and  allowed  to  cool  in  a  vacuum  desiccator.  0-2 — 0-3  gm. 
of  the  dry  silver  salt  is  weighed  into  a  porcelain  crucible  and  gently 
ignited  until  all  organic  matter  is  destroyed,  and  until  the  crucible 
containing  the  residue  of  silver  is  of  constant  weight — care  being  taken 
that  heat  is  not  applied  too  strongly,  since  silver  is  volatile  at  a  high 
temperature. 

The  equivalent  of  the  acid  =  108  f—  °^  ^.;r       —  l) 

\  wt.  oi  silver  / 

and  the  M.W.,  when  monobasic  =108       °^  s^v^r  sa^  _  iq7. 

wt.  oi  silver 

When  the  silver  salt  of  an  acid  is  soluble,  the  calcium  or  barium  salt 
may  be  employed.  These  are  prepared,  either  by  adding  a  soluble 
calcium  or  barium  salt  to  a  soluble  salt  of  the  acid,  or  by  neutralising  the 
acid  itself  with  pure  lime  or  baryta  water.  Ignition  of  a  calcium  salt  is 
carried  out  either  gently  to  the  carbonate,  or  strongly  to  the  oxide.  A 
barium  salt  is  first  ignited  until  decomposition  of  organic  matter  is  com- 
plete, then  cooled  and  converted  into  the  sulphate  by  addition  of  a  few 
drops  of  cone,  sulphuric  acid,  and  finally  ignited  as  sulphate.  Calcium  and 
barium  salts  often  contain  water  of  crystallisation  and  hence  may  require 
great  care  in  drying. 

When  the  sodium  or  potassium  salt  is  available  in  a  pure  state,  a  known 
Jweight  is  ignited  until  only  a  residue  of  pure  carbonate  remains.  A  few 
drops  of  cone,  sulphuric  acid  are  then  carefully  added,  and  heat  from  a 
small  flame  applied  until  the  excess  of  sulphuric  acid  is  driven  off.  If  any 
specks  of  carbon  remain  the  last  process  is  repeated.  Finally  the  residue 
is  weighed  as  alkali  sulphate. 

I  When  an  acid  contains  halogen,  and  the  silver  salt  method  is  employed, 
the  residue  after  ignition  is  treated  with  a  few  drops  of  nitric  acid  and 
a  little  ammonium  halide  to  ensure  complete  conversion  into  silver 
halide. 


474  SYSTEMATIC  ORGANIC  CHEMISTRY 


Determination  of  the  Equivalent  of  a  Base. 

By  Titration. — A  crystalline  salt  of  the  base  with,  some  mineral  or 
organic  acid  is  prepared  and  purified,  and  the  acid  present  in  a  weighed 
quantity  of  the  salt  titrated  with  standard  alkali  (preferably  baryta  solu- 
tion, p.  472)  in  presence  of  phenolphthalein.  From  the  average  of  several 
readings  the  amount  of  the  salt  which  contains  one  equivalent  of  the  acid 
is  calculated,  and  from  this  is  subtracted  the  weight  of  one  equivalent  of 
the  acid,  leaving  the  weight  of  one  equivalent  of  the  base. 

Preparation  and  Decomposition  of  the  Platini-chloride. — Most  organic 
bases  form  well-defined  crystalline  double  salts  with  platinic  and  auric 
chlorides  of  the  general  formulse  BgH^Pt.Clg  and  B2H2AuCl4,  where  B 
represents  one  equivalent  of  the  base.  (Iridio-chlorides  and  cupri-chlorides 
are  sometimes  used.)  These  salts  are  prepared  by  adding  platinic  or 
auric  chloride  to  a  solution  of  the  base  in  dilute  hydrochloric  acid.  The 
double  salt  is  filtered  off,  recrystallised  (generally  from  alcohol),  and  dried 
on  a  porous  plate  in  a  vacuum  desiccator.  When  dry,  a  weighed  quantity 
(0*5 — 1-0  gm.)  is  heated  in  a  porcelain  crucible,  gently  at  first  with  the 
lid  on,  and  afterwards  strongly  until  all  organic  matter  is  burnt  away. 
The  residue  is  weighed  as  platinum  or  gold.  Taking  a  platinum  salt  as 
example,  the  equivalent  weight  of  the  base  is  calculated  as  follows  : — 

M  ,     t         .  t  ,    r  xl     nil  wt.  of  salt  taken  X  195 

Molecular  weight  of  the  double  salt  =  — ;  -e — t—-.  ^ — . 

°  wt.  oi  platinum  residue 

M.W.  of  the  salt  —  409-9  (i.e.,  M.W.  of  H2PtCl6)  =  twice  the  equivalent 
of  the  base.  <C~^) 


CHAPTER  XXXIX 


GROUP  ESTIMATIONS 

Estimation  of  Primary  or  Secondary  Amines  by  Acetylation. 

The  primary  aromatic  amines  are  most  readily  estimated  by  means  of 
♦  nitrous  acid  (see  p.  489).  Primary  or  secondary  amines,  either  alone  or 
in  presence  of  tertiary  amines,  may  be  estimated  by  acetylation,  since  the 
last  do  not  react.  About  1  gm.  of  the  substance  or  mixture  is  weighed 
into  a  small  flask  provided  with  a  reflux  air  condenser,  and  5  c.cs.  of  acetic 
anhydride  added  from  a  pipette  having  a  soda-lime  guard  tube.  In 
another  flask,  also  provided  with  a  similar  condenser,  5  c.cs.  acetic 
anhydride  are  placed.  The  two  flasks  are  allowed  to  stand  at  room  tem- 
perature for  30  minutes  to  1  hour,  after  which  time  50  c.cs.  of  water  are 
added  to  each,  and  both  are  placed  on  the  steam  bath  for  an  hour  in  order 
to  convert  the  remaining  acetic  anhydride  into  acetic  acid.  After  cooling, 
the  amount  of  acetic  acid  in  each  flask  is  titrated  with  standard  sodium 
hydroxide  or  standard  baryta,  using  phenolphthalein  as  indicator.  The 
difference  in  the  two  titrations  corresponds  to  the  amount  of  primary  or 
secondary  amine  present. 

2R.NH2  +  (CH3CO)20  =  2R.NH.COCH3  +  H20 
2R.NH.Ri  +  (CH3CO)20  =  2R.NRi.CO.CH3  +  H20 

The  blank  experiment  is  necessary  since  it  is  difficult  to  obtain  acetic 
anhydride  in  a  pure  state,  and  also  since  there  is  a  slight  loss  of  this 
reagent  from  the  apparatus  during  the  operation.  (For  Xylene  Modi- 
fication, see  C.  Z.,  17,  465.) 

Estimation  of  the  Number  of  Hydroxyl  Groups  in  a  Compound. 

The  acetyl  derivative  (each  hydroxyl  group  acetylated)  is  prepared  and 
purified,  and  a  weighed  quantity  of  it  hydrolysed  with  benzene  sulphonic 
acid.  The  acetic  acid  liberated  is  separated  by  steam  distillation  and 
titrated  with  baryta  solution. 

A  solution  of  pure  benzene  sulphonic  acid  is  prepared  as  follows  : — 
J  100  gms.  of  barium  benzene  sulphonate  (C6H5S03)2Ba  are  recrystallised 
twice  from  distilled  water.  50  gms.  of  the  dry  purified  salt  are  then 
subjected  to  steam  distillation  until  the  distillate  is  no  longer  acid  to 
litmus,  small  amounts  of  volatile  impurities  which  are  generally  present 
in  the  barium  salt  being  thereby  removed.  To  the  hot  liquid  is  added 
the  requisite  amount  (avoiding  excess)  of  pure  sulphuric  acid  necessary 
to  convert  the  barium  salt  into  barium  sulphate  and  benzene  sulphonic 
•acid.  The  barium  sulphate  is  filtered  off  and  washed,  and  the  nitrate  and 
washings  made  up  with  water  to  give  a  10%  solution  of  the  acid. 

475 


476  SYSTEMATIC  ORGANIC  CHEMISTRY 


Example. — Mannitol. — The  hexa-acetyl  derivative  (p.  252)  is  prepared 
and  purified,  and  a  quantity  of  it — about  0-2  gm. — along  with  100  c.cs.  of 
10%  benzene  sulphonic  acid  solution  placed  in  a  steam  distillation  flask. 
The  flask  is  connected  to  a  condenser  on  one  side  and  to  an  apparatus  for 
the  generation  of  pure  steam  on  the  other.  A  suction  flask  to  serve  as 
receiver  is  attached  by  a  cork  to  the  condenser,  and  to  the  side  tube  of  the 
suction  flask  a  soda-lime  tube  to  prevent  the  entrance  of  carbon  dioxide 
is  attached.  Steam  is  blown  through  the  flask  until  (1-5 — 3  hours)  the 
distillate  passing  over  is  neutral.  The  whole  distillate  is  then  titrated 
with  standard  barj^ta,  using  phenolphthalein  as  indicator. 
General  calculation.— 

W  =  weight  of  acetyl  compound 

w  =        ,,      acetic  acid  (by  titration) 


w  X  17 

~60~ 

60 


=        „      OH  =  a 
~\V  —  W  =  corresponding  OH  compound  =  b. 


Then  g  X  100=  percentage  OH 

also     ~  X      —  number  of  OH  groups 

where        M  =  molecular  weight  of  OH  compound. 

It  is  obvious  that  this  method  serves  for  the  estimation  of  acetyl  groups 
present  in  an  alcohol  or  phenol.  It  also  serves  for  the  estimation  of 
acetyl  groups  present  in  a  primary  or  secondary  amine. 

Many  aromatic  phenols  are  more  conveniently  estimated  by  "  coupling  " 
(see  p.  490). 

Estimation  of  Acyl  Derivatives. 

When  the  substance  under  estimation  is  either  an  acyl  derivative  of  an 
alcohol  or  phenol  which  is  not  affected  by  alkali  and  air,  or  an  acyl  deriva- 
tive of  a  volatile  base,  the  estimation  may  be  carried  out  as  for  esters  with 
alcoholic  potash  (p.  524),  any  free  base  being  removed  by  distillation 
before  titrating  the  excess  of  alkali. 

R.O.COKi  +  KOH  =  R.OH  +  K^OOK 
R.NH.COR!  +  KOH  =  K.NH2  +  RjCOOK. 

When  alcoholic  potash  cannot  be  employed,  the  acyl  derivative  may  be 
hydrolysed  with  benzene  sulphonic  acid  (see  above)  or  phosphoric  acid, 
provided  that  the  acid  produced  is  volatile  in  steam  ;  benzene  sulphonic 
acid  is  a  stronger  acid  than  phosphoric. 

Estimation  of  Methoxyl  or  Ethoxyl  Groups. 

All  the  usual  determinations  of  these  groups  are  based  on  the  original 
method  of  Zeisel,  which  consists  in  decomposing  the  substance  with 
hydriodic  acid  thus  : — 

R.(OCH8)x  +  xHI  =  R(OH)x  +  a>CHsI. 
The  resulting  methyl  (or  ethyl)  iodide  is  converted  into  silver  iodide  by 


GROUP  ESTIMATIONS 


477 


the  action  of  alcoholic  silver  nitrate,  and  the  number  of  methoxyl  (or 
ethoxyl)  groups  calculated  from  the  weight  of  silver  iodide,  formed. 

The  hydriodic  acid  used  is  prepared  by  fractional  distillation,  selecting 
for  the  determination  the  fraction  of  constant  B.P.  126°  and  D.  1-68.  The 
alcoholic  silver  nitrate,  which  is  prepared  by  dissolving  4  gms.  of  silver 
nitrate  in  10  c.cs.  of  water  and  adding  90  c.cs.  of  absolute  alcohol,  is 
preserved  in  a  well-stoppered  bottle  in  the  dark,  and  it  should  be  filtered 
and  acidified,  with  one  drop  of  nitric  acid  immediately  before  use. 

The  simplest  modification  of  the  process  is  due  to  Perkin  (J.  C.  S., 
83,  13G7).  The  appara- 
tus employed  is  shown 
in  Fig.  74.  A  Wiirtz 
flask,  having  a  long  neck 
(8  ins.  or  more)  is  used  to 
contain  the  mixture  of 
substance  and  hydriodic 
acid ;  the  flask  is  im- 
mersed in  a  glycerine 
bath  in  such  a  manner 
that  the  side  tube  is 
tilted  upwards  to  serve 
as  a  reflux  condenser ; 
and  through  the  cork  in 
the  neck  of  the  flask 
there  passes  a  carbon 
dioxide  delivery  tube 
reaching  almost  to  the 
surface  of  the  reaction 
mixture.  The  side  tube 
of  the  Wiirtz  flask  is 
connected  to  two  smaller 
flasks,  the  first  of  which 
contains  20  c.cs.  and  the 
second  15  c.cs.  of  alco- 
holic silver  nitrate.  The 

connecting  tube  between  these  two  flasks  acts  as  a  syphon,  dipping  just 
below  the  liquid  in  the  second  flask  and  reaching  just  above  the  liquid  in 
the  first  flask. 

0-2 — 0-3  gm.  of  the  substance  is  weighed  and  placed  in  the  Wiirtz  flask, 
and  15  c.cs.  of  hydriodic  acid  of  D.  1-68,  along  with  a  few  porcelain  chips 
added.  The  cork  bearing  the  delivery  tube  is  replaced  in  the  neck  of  the 
flask,  and  a  slow  current  of  carbon  dioxide,  purified  by  passing  first 
through  aqueous  silver  nitrate  and  then  through  cone,  sulphuric  acid,  is 
forced  through  the  apparatus.  The  temperature  of  the  glycerine  bath  is 
raised  to  130°  or  140°,  the  first  temperature  being  for  methoxyl  compounds, 
and  the  second  for  ethoxyl  compounds.  When  the  upper  portion  of  the 
liquid  in  the  first  small  flask  remains  perfectlv  clear  after  the  resultant 
silver  iodide  has  settled,  the  temperature  of  the  glycerine  bath  is  raised 


Fig.  74. 


478  SYSTEMATIC  ORGANIC  CHEMISTRY 


until  the  hydriodic  acid  boils  gently,  and  it  is  kept  thus  for  an  hour.  The 
silver  nitrate  flasks  are  then  replaced  by  the  V-shaped  tube  containing  a 
few  c.cs.  of  alcoholic  silver  nitrate,  and  the  heating  continued  for 
15  minutes.  If  no  precipitate  forms  the  operation  is  finished,  but  if  a 
precipitate  forms,  the  liquid  in  the  V-tube  is  added  to  the  contents  of  one 
of  the  small  flasks  and  replaced  by  fresh  alcoholic  silver  nitrate,  the  heating 
being  continued  for  another  15  minutes,  and  so  on  until  no  more  alkyl 
iodide  passes  over. 

The  contents  of  the  two  small  flasks  are  diluted  with  water,  allowed  to 
stand  for  5  minutes  to  ensure  decomposition  of  the  last  traces  of  alkyl 
iodide,  and  finally  poured  gradually  into  50  c.cs.  of  boiling  water  acidified 
with  nitric  acid,  which  is  boiled  until  the  alcohol  is  driven  off.  The  pre-, 
cipitate  is  collected  in  a  weighed  Gooch  crucible,  washed,  and  dried  in  an 
air  oven  at  120°.    The  percentage  is  calculated  as  follows  : — 


Methoxvl 


Ethoxyl 


wt.  of  silver  iodide 
wt.  of  substance 

wt.  of  silver  iodide 
wt.  of  substance 


X 


3102 
234-9 
4504 
234-9 


Cummings  Modification.  (J.  S.  C.  I.,  41,  20.)— A  convenient  appa- 
ratus for  the  estimation  of  methoxyl  groups  by  the  Zeisel  method  is 

that  used  by  Robertson  for  the  esti- 
mation of  halogens  (p.  461).  This 
consists  of  a  long-necked  round- 
bottomed  flask  attached  by  a  ground- 
glass  joint  to  a  bulbed  U-tube.  The 
methyl  iodide  generated  by  the  inter- 
action of  hydriodic  acid  and  the 
methoxy  group  is  absorbed  in  alco- 
holic silver  nitrate.  Pyridine  may 
also  be  used  as  absorbent  (J.  C.  S., 
117,  193). 

The  apparatus  shown  in  the  sketch 
(Fig.  75)  gives  very  good  results. 

The  flask  is  of  250  c.cs.  capacity, 
and  its  neck,  from  bulb  to  the  ground- 
glass  joint,  25  cms.  long.  The 
delivery  tube,  to  which  is  fixed  a  side 
tube,  is  attached  to  the  flask  by  means 
of  a  ground-glass  joint.  A  thermo- 
meter is  fixed  as  shown  with  its  bulb  opposite  the  delivery  exit.  To  the 
delivery  tube  is  attached  also  by  a  ground-glass  joint  an  absorber  which 
contains  about  10—15  c.cs.  of  pyridine.  The  apparatus  is  easily  filled, 
emptied  and  washed. 

When  the  apparatus  is  in  use,  the  bulb  of  the  flask  containing  the 
hydriodic  acid  and  the  substance  is  heated  in  a  water  bath  at  100°  C. 
The  methyl  iodide  is  carried  over  into  the  absorber  by  a  slow  current  of 


Fig.  75. 


GROUP  ESTIMATIONS 


479 


dry  carbon  dioxide,  passing  in  at  the  side  tube.  The  temperature  on  the 
thermometer  should  not  be  higher  than  35° — 40°  C.  for  methoxy,  and 
40°  C.  for  ethoxy  compounds.  At  these  temperatures  no  hydriodic  acid 
is  distilled  over.  As  a  further  precaution,  the  neck  of  the  flask  is  slanted 
away  from  the  source  of  heat. 

The  absorption  is  complete  in  about  one  hour.  The  pyridine  and  its 
methiodide  are  then  washed  out  with  water,  acidified  with  nitric  acid, 
a  known  volume  of  silver  nitrate  added  and  the  excess  of  the  latter 
estimated  by  thiocyanate,  using  ferric  alum  as  indicator. 

Estimation  of  Esters. 

1.  By  hydrolysis  with  standard  alcoholic  potash.  A  weighed  quantity, 
1 — 2  gms.,  of  the  ester  is  placed  in  a  flask  containing  50  c.cs.  of  semi- 
normal  alcohol  potash.  The  flask  is  fitted  with  a  reflux  condenser,  and 
the  mixture  boiled  on  a  water  bath  for  2 — 3  hours  until  hydrolysis  is 
complete.    A  little  water  is  then  run  down  the  inner  surface  of  the  con- 

I  denser  into  the  flask,  and  the  excess  of  potash  in  the  flask  titrated  with 
standard  hydrochloric  acid,  using  Methyl  Orange  as  indicator.  The 
quantity  of  potash  used  in  the  hydrolysis  gives  a  measure  of  the  value  of 
the  ester  (see  p.  524). 

R-COORi  +  KOH  ==  R.COOK  +  RiOH. 

2.  By  use  of  benzene  sulphonic  acid  or  phosphoric  acid.  When  the 
ester  yields  on  hydrolysis  products  which  become  coloured  in  presence  of 
alkali  and  air,  the  above  method  is  inapplicable.  If  the  acid  produced  on 
hydrolysis  is  volatile  in  steam,  benzene  sulphonic  or  phosphoric  acid  may 
be  used  as  hydrolytic  agent,  and  the  acid  (from  the  ester)  after  separation 
by  steam  distillation  is  titrated  with  standard  alkali.  (See  Estimation  of 
Acetyl  Group,  p.  476.) 

Estimation  of  Amides. 

Amides  are  estimated  by  hydrolysis  with  alkalis  (generally  aqueous  or 
alcoholic  potash)  or  with  acids  (sulphuric,  phosphoric  or  benzene  sulphonic). 
In  the  former  case  the  ammonia  set  free  is  absorbed  in  standard  acid  (as 
in  the  Kjeldahl  estimation  of  nitrogen)  and  the  excess  of  acid  titrated. 
In  the  latter  the  estimation  is  conducted  similarly  to  a  Kjeldahl 
estimation  of  nitrogen,  the  ammonium  salt  formed  on  hydrolysis  being 
afterwards  decomposed  by  alkali  and  the  liberated  ammonia  collected 
in  standard  acid. 

Estimation  of  Aldehydes  (other  than  Formaldehyde). 

The  method  depends  on  the  combination  of  alkali  bisulphites  with 
aldehydes. 

25  c.cs.  of  the  solution  to  be  examined,  which  must  not  contain  more 
|  than  0-5%  of  total  aldehyde,  are  run  into  50  c.cs.  of  a  solution  of  potassium 
j  bisulphite  containing  12  gms.  of  KHS03  per  litre,  placed  in  a  150-c.c. 
flask  which  is  then  well  corked  and  allowed  to  stand  for  15  minutes. 


480  SYSTEMATIC  ORGANIC  CHEMISTRY 


During  this  time  another  50  c.cs.  of  the  potassium  bisulphite  solution  is 
N  . 

titrated  with      iodine.    The  excess  of  bisulphite  added  to  the  aldehyde 

solution  is  then  determined  with  the  same  iodine,  and  from  the  difference 
the  bisulphite  absorbed  by  the  aldehyde,  and  hence  the  aldehyde  present 
can  be  calculated.  The  strength  given  for  the  bisulphite  solution  should 
be  adhered  to,  otherwise  the  quantities  of  hydriodic  acid  liberated  in  more 
concentrated  solutions  reduce  the  sulphuric  acid  formed — the  reverse 
reaction  coming  into  play.  The  bisulphite  method  gives  an  accurate 
figure  also  for  dilute  solutions  of  mixed  aldehydes  ;  combining  it  with  the 
cyanide  method  (see  p.  481),  the  amount  of  formaldehyde  and  of  another 
aldehyde  in  a  solution  of  the  two  can  be  estimated. 

N 

1  c.c.  ~r  iodine  =  1-5  mgs.  CH20 

-  2-2  mgs.  CH3.CHO 

mol.  wt.  of  aldehyde  in  enxis. 

=  20   —  mgs- 

Aldehydes  insoluble  in  water  should  be  dissolved  in  dilute  alcoholic 
solution,  the  concentration  of  alcohol  being  kept  below  5%. 

Estimation  o£  Formaldehyde. 

Many  methods  are  available  for  the  estimation  of  formaldehyde. 

1.  For  pure  dilute  solutions  the  following  is  recommended.  10  c.cs.  of 
the  formaldehyde  solution  which  must,  if  necessary,  be  diluted  so  that  it  is 
not  more  than  a  2%  solution,  is  mixed  with  25  c.cs.  of  N/10  iodine  solution. 
10%  caustic  soda  solution,  pure  and  free  from  nitrite,  is  added,  with 
shaking,  drop  by  drop  from  a  burette  until  a  clear  yellow  liquid  is 
obtained ;  after  standing  for  10  minutes,  an  equal  quantity  of  10% 
hydrochloric  acid,  plus  an  extra  5  c.cs.,  is  added  to  liberate  the  excess 

N 

of  iodine  which  is  back  titrated  with  ^  thiosulphate  using  freshly 
made  starch  paste  as  indicator. 

N 

1  c.c.  jq  iodine  =  1-5  mg.  formaldehyde 
6NaOH  +  3I2  =  NaI03  +  5NaI  +  3H20 
3  CH20  +  NaI03  =  3CH202  +  Nal 
5NaI  +  NaI03  +  6HC1  =  6NaCl  +  3I2  +  3H20. 

This  method  is  very  satisfactory  for  formaldehyde  provided  other 
aldehydes  be  absent.    In  a  solution  containing  1  gm.  CH20  per  litre,  two 

N 

titrations  should  not  differ  by  more  than  0-1  c.c.  of  —  thiosulphate  and 

the  method  will  show  1  part  of  formaldehyde  in  100,000  parts  of  water. 
It  is  necessary  for  such  consistency  that  the  quantities  of  acid  and  alkali 
employed  be  carefully  controlled  as  described  ;  on  no  account  must  a 


GROUP  ESTIMATIONS 


481 


great  excess  of  alkali  be  used,  as  there  then  is  a  danger  of  some  of  the 
formaldehyde  being  converted  to  iodoform. 

2.  For  impure  dilute  solutions  of  formaldehyde,  especially  those  con- 
taining other  aldehydes,  the  cyanide  method  should  be  used.  The  iodine 
method  is  not  reliable  in  this  case,  as  all  aldehydes  present  are  attacked. 
But  while  aldehydes,  other  than  formaldehyde,  combine  similarly  with 
potassium  cyanide  in  the  cold,  they  do  so  slowly ;  if  the  excess  of  cyanide 
is  removed  immediately  with  silver  nitrate,  only  formaldehyde  is  esti- 
mated. The  addition  product  of  formaldehyde  and  potassium  cyanide 
reduces  silver  nitrate  in  the  cold.  If  the  silver  nitrate  solution,  however, 
be  acidified  with  nitric  acid  before  adding  the  aldehyde-cyanide  mixture, 
no  precipitate  results  if  the  aldehyde  in  the  latter  be  in  excess.  If  the 
cyanide  be  in  excess,  1  mol.  of  formaldehyde  combines  with  1  mol.  of 
cyanide,  whilst  the  excess  precipitates  silver  cyanide  from  the  silver 
nitrate  solution  in  the  usual  way. 

N 

The  details  are  as  follows  :  10  c.cs.  of      silver  nitrate  acidified  with 

6  drops  of  50%  nitric  acid  are  mixed  with  10  c.cs.  of  potassium  cyanide 
solution  (prepared  by  dissolving  3-1  gms.  of  96%  salt  in  500  c.cs.  distilled 
water),  the  whole  diluted  to  50  c.cs.,  well  shaken,  filtered,  and  25  c.cs.  of 

N 

the  nitrate  titrated  with  ^  ammonium  thiocyanate.    Another  10  c.cs.  of 

the  potassium  cyanide  solution,  to  which  10  c.cs.  of  the  aldehyde  solution 
has  just  been  added,  are  run  in,  the  whole  made  up  to  50  c.cs.,  shaken, 
rapidly  filtered,  and  25  c.cs.  of  the  filtrate  immediately  titrated  as  before. 
The  difference  between  this  and  the  blank  titration  gives  the  amount  of 
potassium  cyanide  not  precipitated  by  the  formaldehyde. 

N 

1  c.c.      thiocyanate  =  3  mgs.  CH20 
CH20  +  KCN  =  KO.CH2CN. 


s.o.c. 


CHAPTER  XL 


Estimations  based  on  the  Use  of  Titanous  Chloride. 

This  energetic  reducing  agent  can  be  maintained  at  constant  strength 
in  aqueous  hydrochloric  acid  solution  for  a  reasonable  period.  It  is 
advisable,  however,  to  re-standardise  it  after  24  hours'  standing.  It  serves 
for  the  reduction  of  aromatic  nitro  compounds,  some  nitroso  bodies,  many 
azo  dyes  and  of  nearly  all  the  dyes  which  yield  leuco-compoimds.  It  is 
easily  standardised  against  a  ferric  salt— say  ferric  alum — using  potassium 
thiocyanate  as  indicator.    The  equation — ■ 

TiCl3  +  FeCl3  =  TiCl4  +  FeCl2 

shows  that  1  mol.  titanous  chloride  is  equivalent  to  56  gms.  iron,  and  also 

that  its  abilitv  to  reduce 


A 


"HI 


is  due  to  the  metal  (Ti) 
passing  from  the  tri-  to 
the  tetra-valent  condi- 
tion. 

Preparation  and  Stor- 
age of  Titanous  Chloride 
Solution  for  Analysis. — 

50  c.cs.  of  the  commer- 
cial titanous  chloride 
solution  (20%)  are 
boiled  with  100  c.cs.  of 
cone,  hydrochloric  acid 
for  1  minute,  and  then 
made  up  to  about  2 
litres  in  a  storage  bottle 
A  (Fig.  76).  The  solu- 
tion when  freshly  pre- 
pared, should  fill  the 
bottle  completely; 
otherwise  air  remains 
which  must  be  displaced 
by  hydrogen.  A  is  con- 
nected to  both  top  and 
bottom  of  a  burette  by 
means  of  glass  and 
rubber  tubing.  The 
burette  has  a  2-way 
glass  stopcock  at  B,  so  that  it  can  receive  solution  from  A,  or  deliver  solu- 


Iff' 


Fig. 


tion  through  its  orifice. 


The  second  tube  from  the  top  of  A  leads  to  a 

482 


ESTIMATIONS  BASED  ON  USE  OF  TITANOUS  CHLORIDE  483 


hydrogen  generator  H,  which  consists  of  2  parts,  (a)  an  inner  tube,  made  by- 
drawing  a  test-tube  out  to  a  fine  point ;  this  contains  granulated  zinc,  and 
is  connected  by  means  of  a  rubber  stopper  and  delivery  tube  to  A  ;  (b)  an 
outer  vessel  containing  hydrochloric  acid  (15%).  To  replace  all  the  air  in 
the  apparatus  by  hydrogen,  the  stopcock  is  turned  to  allow  solution  from 
A  to  fill  the  tube  leading  to  the  bottom  of  the  burette.  The  stopcock 
is  then  turned  as  for  delivery  from  the  burette,  and  hydrogen  allowed  to 
escape  from  the  apparatus  for  5  minutes.  The  burette  is  filled,  emptied 
and  refilled,  after  which  the  apparatus  is  ready  for  use. 

Standardisation. — 3-5  gms.  of  pure  ferrous  ammonium  sulphate  are 
dissolved  in  distilled  water,  100  c.cs.  of  5N  sulphuric  acid  added,  and  the 
whole  made  up  to  250  c.cs.    25  c.cs.  of  this  are  oxidised  with  potassium 

N 

permanganate  solution  of  approximately  —  strength,  until  a  faint  pink 

ou 

colour  persists.  A  large  excess  of  potassium  thiocyanate  (0*2— -0-3  gm.) 
is  added,  and  titan ous  chloride  solution  run  in  from  the  burette  until  the 
red  colour  due  to  ferric  thiocyanate  just  disappears.  If  25  c.cs.  of  iron 
solution  require  x  c.cs.  of  titanous  chloride  solution  to  reduce  it,  then 

each  c.c.  of  the  latter  is  equivalent  to— ^  gm.  iron. 

A  solution  of  iron  alum,  containing  about  14  gms.  per  litre,  and  acidified 
with  sulphuric  acid  until  the  solution  assumes  a  pale  straw  colour,  is  pre- 
pared. By  titrating  25  c.cs.  of  this  with  titanous  chloride,  using  potassium 
thiocyanate  as  indicator,  its  strength  is  determined,  and  as  it  will  retain 
its  strength  for  a  long  period,  this  alum  solution  may  be  used  in  all 
subsequent  cases  for  standardising  the  titanous  chloride  solution. 

Nitro  Compounds. — (a)  Those  Soluble  in  Water.— A  known  amount  of 
nitro-body  is  dissolved  in  water  in  a  conical  flask,  hydrochloric  acid  is  added, 
and  the  solution  is  boiled  with  a  stream  of  carbon  dioxide  passing  through. 
Heating  is  momentarily  stopped,  and  a  large  excess  of  titanous  chloride 
solution  run  in.  The  contents  are  boiled  for  10  minutes  to  ensure  complete 
reduction.  Carbon  dioxide  is  passed  through  the  flask  during  the  entire 
operation.  The  solution  is  then  cooled  and  the  excess  of  titanous  chloride 
determined  by  titration  with  ferric  alum  solution,  using  potassium  thio- 
cyanate as  indicator.  A  control  experiment  without  nitro  compound  present 
is  performed  under  exactly  the  same  conditions.  6  equivalents  of  titanous 
chloride  (6  H  atoms)  are  required  for  the  reduction  of  each  N02  group. 

Example. — 0-4979  gm.  ^-nitraniline  is  dissolved  in  hydrochloric  acid 
on  the  water  bath,  and  made  up  to  500  c.cs.  20  c.cs.  of  this  solution  are 
reduced  with  50  c.cs.  titanous  chloride  as  described  above,  and  the 
excess  of  the  latter  titrated  back  with  ferric  alum.  Excess  TiCl3  =  9-7  c.cs. 
A  control  experiment  having  no  ^-nitraniline  used  0-76  c.c.  TiCl3. 

TiCl3  used  =  39-54  c.cs.    1  c.c.  TiCl3  =  0-0012228  gm.  Fe. 

138  ^-mtraniline  require  336  Fe. 

A  Aa~a             ,  •     0-0012228  X  39-54  X  138  X  25      .  „. 
.*.  0-4979  gm.  contains  -   ^—^ —  -  ^-nitramhne 

=  99-7%. 

i  i  2 


484  SYSTEMATIC  ORGANIC  CHEMISTRY 


Picric  acid  and  Naphthol  Yellow  S  may  be  estimated  in  a  similar 
manner. 

(b)  Those  insoluble  m  water  mnst  first  be  sulphonated  by  beating  with 
20  parts  by  weight  of  fuming  sulphuric  acid  on  a  water  bath  for  2  hours. 
The  product  is  then  made  up  to  a  definite  volume  with  water  and  an  aliquot 
part  titrated  with  titanous  chloride  as  described  for  soluble  nitro  com- 
pounds. 

Example. — 1-01  gms.  nitrobenzene  are  sulphonated  as  described  above, 
then  cooled  and  the  volume  carefully  made  up  to  1  litre.  20  c.cs.  are  with- 
drawn and  reduced  with  50  c.cs.  TiCl3  solution  (as  for  ^-nitraniline). 

Excess  TiCl3  =  18  c.cs.    Control  experiment  =  0-8  c.c.  TiCl3. 

Vol  TiCl3  used  =  31-2  c.cs.  =  31-2  X  0-001700  gm.  Fe. 

123  nitrobenzene  =  336  Fe 

'  .   0-0017  X  31-2  X  123  X  50     .  Q7AQ 
.-.  1-002  gms.  contain  ^  =0  -9709 

=  96-1%. 

(c)  Nitro  compounds  insoluble  and  yet  not  easily  sulphonated,  e.g., 
dinitrobenzene  or  dinitronaphthalene,  are  dissolved  in  alcohol,  and  the 
solution  poured  into  a  known  volume  of  titanous  chloride  solution  acidified 
with  hydrochloric  acid,  through  which  carbon  dioxide  is  passed.  The 
mixture  is  boiled,  allowed  to  cool,  and  the  excess  of  titanous  chloride 
estimated  with  ferric  alum. 

Example. — 0-110  gm.  commercial  dinitronaphthalene  is  dissolved  in 
250  c.cs.  alcohol.  50  c.cs.  TiCl3  solution  are  placed  in  a  conical  flask, 
10  c.cs.  cone.  HC1  added,  carbon  dioxide  passed  through,  and  25  c.cs. 
of  the  dinitronaphthalene  solution  run  in.  The  mixture  is  boiled,  then 
allowed  to  cool,  and  the  excess  of  TiCl3  titrated. 

Excess  TiCl3  =  31-60  c.cs.    Control  experiment     0-90  c.c.  TiCl3. 

Vol.  TiCl3  used  =  17-5  c.cs.  =  17-5  X  0-001750  Fe. 

218  dinitronaphthalene  =  672  Fe. 

mm  /•  0-00175  x  17-5  x  10  x  218  .  nonQQ 
0-110  gm.  contains   ^   =  0-09933 

=  90-3%. 

Nitroso  Compounds. — Owing  to  the  intense  colour  which  these  com- 
pounds yield  in  hydrochloric  acid  solution  they  may  be  titrated  directly 
with  titanous  chloride  until  the  yellow  colour  disappears.  A  weighed 
quantity  is  dissolved  in  hydrochloric  acid  and  made  up  to  a  known 
volume.  An  aliquot  part  of  this  solution  is  warmed  to  40° — 50°  in  a 
conical  flask  with  carbon  dioxide  passing  through,  and  titanous  chloride 
solution  is  run  in  until  the  yellow  colour  disappears.  4  equivalents  of 
titanous  chloride  are  required  for  each  nitroso  group. 

Example. — 1-005  gms.  nitrosodimethy] aniline  are  dissolved  in  20  c.cs. 


ESTIMATIONS  BASED  ON  USE  OF  TITANOUS  CHLORIDE  485 

cone,  hydrochloric  acid  and  sufficient  water  to  make  volume  up  to  500  c.cs. 
10  c.cs.  of  this  solution  required  17-5  c.cs.  TiCl3  solution. 

1  c.c.  TiCl3  =  0-001700  gm.  Fe. 
150  nitrosodimethvlaniline  =  224  Fe. 

.-.  1-005  gms.  contain  -  ^  =  0-9983  gm. 

=  99-3%. 

Azo  Dyes. — (1).  Azo  dyes  which  are  soluble  in  dilute  hydrochloric  acid 
may  be  titrated  directly,  the  disappearance  of  the  colour  indicating  the 
end  point. 

(2)  .  Many  azo  dyes  which  are  insoluble  in  dilute  hydrochloric  acid 
can  be  titrated  directly  in  presence  of  Rochelle  salt.  Since  Rochelle  salt 
forms  a  compound  with  titanium,  which  is  pale  yellow  in  dilute  solution, 
this  method  is  inapplicable  for  the  estimation  of  yellow  dyes. 

(3)  .  A  number  of  azo  dyes  which  cannot  be  estimated  according  to  (1)  or 
(2),  may  be  estimated  indirectly.  A  weighed  quantity  of  dye  is  boiled  in 
aqueous  solution  in  a  flask  through  which  a  stream  of  carbon  dioxide 
is  passing.  After  adding  hydrochloric  acid  an  excess  of  titanous 
chloride  is  run  into  the  boiling  mixture.  The  reduction  is  usually  complete 
in  about  2  minutes,  after  which  the  flask  is  cooled  under  the  tap  with  the 
current  of  carbon  dioxide  still  passing.  When  cold,  the  excess  of  titanous 
chloride  is  estimated  with  ferric  alum  solution  using  potassium  thio- 
cyanate  as  indicator.  The  azo  group  requires  4  equivalents  of  titanous 
chloride. 

Example  of(l). — 1-003  gms.  of  Orange  II.  (C16HnN204SNa)  are  dissolved 
in  water  and  made  up  to  500  c.cs.  50  c.cs.  are  withdrawn  into  a  conical 
flask,  5  c.cs.  cone,  hydrochloric  acid  added,  and  after  boiling  for  1  minute, 
titrated  with  titanous  chloride. 

Vol.  TiCl3  required  =  29-15  c.cs.  =  29-15  X  0-00165  gm.  Fe. 

350  Orange  II.  =  224  Fe. 

i  aaq              4.  •  29-15  X  0-00165  X  10  X  350      .  _no 
.-.  1-003  gms.  contain   ^24  =  0*7522  gm. 

=  75%. 

Example  of  (2). — 1-10  gms.  of  Diamine  Black  (C34H24014N6S4Na4)  are 
dissolved  in  250  c.cs.  water.  50  c.cs.  of  this  solution  are  withdrawn, 
25  c.cs.  of  Rochelle  salt  solution  (about  20%)  added,  and  titrated  with 
titanous  chloride  until  the  colour  of  the  dye  disappears. 

Vol.  TiCl3  used  =  20-22  c.cs.  =  20-22  X  0-00165  gm.  Fe. 
960  diamine  black  =  448  Fe. 

-  1A                    20-2  X  0-00165  X  5  X  960      .  ,  . 
.-.  1-10  gms.  contain  —r^  —  =  0-44  gm. 

=  40%. 

Example  of  (3). — 0-99  gm.  of  Chrysophenine  G  (C30H26N40gS2Na2)  is 


486 


SYSTEMATIC  ORGANIC  CHEMISTRY 


dissolved  in  a  litre  of  water.  100  c.cs:  of  this  solution  are  withdrawn  and 
boiled,  with  a  current  of  carbon  dioxide  passing  through  ;  10  c.cs.  of  cone, 
hydrochloric  acid  and  50  c.cs.  of  titanous  chloride  are  then  added,  and 
the  mixture  boiled  until  the  precipitate  dissolves  and  the  solution  turns  a 
slight  violet  colour.  After  cooling,  the  excess  of  titanous  chloride  is 
titrated  with  ferric  alum. 

Excess  TiCl3  =  34-2  c.cs. 
Vol.  TiCl3  used  =  15-8  c.cs.  =  15-8  X  0-00165  gm.  Fe. 

680  chrysophenine  =  448  Fe. 

,  .     15-8  X  0-00165  X  10  X  680     ft  w 

.-.  0-99  gm.  contains  j-^  =  0-396  gm. 

&  448  & 

=  40%. 

Dyes  which  Yield  Colourless  Leuco  Compounds. — Approximately  1  gm. 
is  dissolved  in  250  c.cs.  water  ;  50  c.cs.  of  this  solution  and  about  2  c.cs. 
cone,  hydrochloric  acid  are  introduced  into  a  conical  flask  fitted  with  a 
rubber  stopper  having  3  holes.  Through  one  hole  a  current  of  carbon 
dioxide  is  introduced,  another  serves  for  the  escape  of  this  gas,  and  the 
third  is  left  for  the  delivery  tube  of  the  titanous  chloride  burette.  The 
solution  is  boiled,  and  then  titrated  with  titanous  chloride,  until  the 
colour  just  disappears. 

Example. — 1  gm.  crystallised  zinc-free  Methylene  Blue  (C16H18N3S,C1) 
is  treated  as  described  above.  50  c.cs.  of  this  solution  required  41-64  c.cs. 
titanous  chloride  solution,  of  which  1  c.c.  =  0-00165  gm.  Fe. 

319-5  Methylene  Blue  =  112  Fe. 

,  .      41-6  X  0-00165  X  5  X  319-5      .  no 

/.  1  gm.  contains  — ^  =  0-98  gm. 

11^ 

=  98  %. 

The  zinc  double  chloride  of  Methylene  Blue  has  the  formula  2C16H18N3. 
S.C1,  ZnCl2,  H20,  and  is  much  less  soluble  in  dilute  hydrochloric  acid.  A 
drop  of  weak  Methylene  Blue  solution  may  be  used  as  indicator  in  the 
direct  titration  of  substances  with  titanous  chloride  where  a  selective 
reduction  takes  place.  The  end  point  is  perfectly  sharp  if  the  solution 
is  warmed  to  35°. 

Of  other  examples  which  yield  leuco  compounds,  Indigo  may  be  esti- 
mated by  titrating  the  sulphonated  dye  in  presence  of  Rochelle  salt : 
Magenta  in  Rochelle  salt  solution ;  Eosin  and  Rhodamine  in  presence  of 
Rochelle  salt  and  alcohol,  the  latter  to  keep  the  leuco  compound  in 
solution.  All  these  titrations  are  carried  out  on  the  boiling  dye  solution 
and  in  presence  of  carbon  dioxide. 

For  many  other  valuable  applications  of  the  use  of  titanous  chloride, 
see  Knecht  and  Hibbert,  "  New  Reduction  Methods  in  Volumetric 
Analysis"  (Longmans,  Green  &  Co.). 


CHAPTER  XLI 

ESTIMATIONS  BASED  ON  DIAZOTISATION  OR  COUPLING. 

Preparation  of  Standard  Reagents. 

(a)  Sodium  Nitrite. — Sodium  nitrite  is  often  estimated  by  the  use  of 
permanganate  and  oxalic  acid.  When  impure  sodium  nitrite  is  estimated 
in  this  manner,  the  values  obtained  are  often  too  high,  owing  to  the 
presence  of  other  oxidisable  substances.  For  reactions  such  as  those 
which  follow,  it  should  be  estimated  with  pure  sulphanilic  acid  or  with 
pure  benzidine. 

Commercial  sulphanilic  acid  is  purified  by  dissolving  in  sufficient  aqueous 
sodium  carbonate  to  give  an  alkaline  solution,  which  is  boiled  until  all 
trace  of  aniline  disappears.  The  solution  is  filtered  and  acidified  with 
hydrochloric  acid,  and  after  12  hours  the  product  is  filtered  off  and  washed 
with  a  little  water.  It  is  again  dissolved  by  means  of  hot  water  and 
sodium  carbonate  to  a  neutral  solution  ;  the  solution  is  quickly  cooled 
along  with  stirring  to  0°,  and  the  sodium  sulphanilate  filtered  off.  These 
crystals  are  dissolved  in  distilled  water,  and  acidified  with  pure  cone, 
hydrochloric  acid.  The  crystals  which  separate  are  filtered  off  and 
washed  free  of  sodium  chloride  with  distilled  water  ;  they  are  once  more 
recrystallised  from  distilled  water,  and  afterwards  dried  until  of  constant 
weight  in  an  air  oven  at  120°.  The  product  should  be  preserved  in  a  bottle 
having  a  ground-glass  stopper.  To  prepare  a  semi-normal  solution, 
exactly  86-5  gms.  are  dissolved  in  50  c.cs.  pure  (20%)  ammonia,  and  made 
up  to  1  litre  ;  the  solution  when  preserved  in  the  dark  will  keep  for  many 
months. 

To  prepare  semi-normal  nitrite  solution,  about  37*5  gms.  of  commercial 

sodium  nitrite  (or  rather  less  of  the  purer  salt)  are  dissolved  in  water, 

N  N 
filtered,  and  made  up  to  1  litre.    50  c.cs.  of  the     sulphanilic  acid  or 

benzidine  solution  are  then  titrated  with  it  in  the  following  manner  : — 

The  solution  is  measured  by  means  of  a  pipette  into  a  500-c.c.  beaker  ; 
200  gms.  of  ice  and  13  gms.  of  cone,  hydrochloric  acid  are  also  added.  The 
beaker  is  slightly  tilted  to  one  side,  and  the  nitrite  solution,  run  in  from  a 
burette,  is  allowed  to  trickle  down  the  side  of  the  beaker  and  thus  to  sink 
quickly  to  the  bottom.  When  about  45  c.cs.  nitrite  have  been  added,  the 
solution  is  stirred  with  a  glass  rod,  and  more  nitrite  is  run  in,  drop  by  drop, 
(tests  being  carried  out  at  intervals),  until  a  drop  of  the  solution  just 
causes  an  immediate  blue  coloration  on  starch-iodide  paper.*  After 

*  A  certain  amount  of  practice  is  necessary  to  judge  the  end  point 
accurately,  as  the  paper  when  moistened  with  diazonium  solution  generally 

487 


488  SYSTEMATIC  ORGANIC  CHEMISTRY 


standing  a  few  minutes,  a  test  is  again  applied  to  see  if  the  excess  of  nitrite 
still  remains,  and  if  not,  more  nitrite  is  added,  until  a  slight  positive  test 
is  obtained  after  a  few  minutes'  standing.  It  is  advisable  to  repeat  the 
operation,  all  but  1  c.c.  of  the  total  volume  of  nitrite  used  in  the  previous 
test  being  run  in  at  once  along  the  side  of  the  beaker ;  this  obviates  as 

much  as  possible  the  escape  of  free 
nitrous  acid  on  mixing.  The 
remainder  of  the  nitrite  is  run  in, 
drop  by  drop,  as  before.  From  the 
volume  of  nitrite  necessary,  a  cal- 
culation is  made  to  ascertain  what 
volume  of  water  must  be  added  to 
make  the  remaining  nitrite  exactly 
semi-normal. 

Fig.  77  shows  a  convenient  type 
of  burette  for  use  in  cases  where 
many  titrations  have  to  be  per- 
formed. The  burette  is  fixed  to 
the  storage  bottle  and  the  liquid 
is  blown  up  into  the  burette  by 
compressed  air  from  the  hand  bulb, 
the  bead  at  A  being  opened  by 
pressure  between  the  fingers.  The 
titration  is  done  at  C  by  opening 
the  bead  at  B. 


N 


Aniline  Solution. — About 


Fig.  77. 


250  c.cs.  of  the  purest  commercial 
aniline  are  carefully  redistilled,  and 
the  fraction  passing  over  within 
half  a  degree  at  its  boiling  point 
reserved  for  the  preparation  of  the 
standard  solution.  Exactly  4-6-5 
gms.  of  the  above  fraction  are 
weighed  ;  to  this  is  added  50  c.cs. 
ice-water,  and  75  c.cs.  of  cone, 
hydrochloric  acid,  the  object  of 
the  ice-water  being  to  prevent  the 
escape  of  fumes  when  the  acid  and  amine  come  together.  The  solution 
is  then  made  up  to  1  litre  with  distilled  water ;  when  prepared  in  this  way, 
it  is  generally  accepted  as  exactly  semi-normal,  and  many  use  it  as  such 
for  the  standardisation  of  sodium  nitrite  solution  ;  however,  if  any  doubt 

exists,  it  is  standardised  against  the  previously  prepared     sodium  nitrite. 

develops  a  blue  colour  on  standing  a  short  time.  Approaching  the  end  point 
the  eye  detects  a  brief  interval  between  the  moistening  of  the  test  paper  and 
the  development  of  the  colour ;  at  the  end  point  this  interval  disappears  and 
the  colour  develops  instantaneously. 


ESTIMATIONS  BASED  ON  DIAZOTISATION  OR  COUPLING  489 


N  N 

(c)  2q  Phenyldiazonium  Solution. — 50  c.cs,  of  the      aniline  solution 

are  measured  out  into  a  500-c.c.  flask,  25  c.cs.  of  cone,  hydrochloric  acid 

are  added,  and  the  flask  immersed  in  ice- water.    When  thoroughly  cold, 

N  . 
50  c.cs.  of  ^  sodium  nitrite  are  run  in  from  a  burette,  the  contents  of  the 

flask  being  gently  rotated  at  intervals.    After  standing  for  15  minutes,  the 
solution  is  made  up  to  500-c.c. ;  it  may  be  preserved  for  a  few  hours  at  0° 
in  the  dark,  but  should  always  be  freshly  prepared  for  use. 
N 

(d)  —  R  Salt  Solution. — 20  gins,  of  commercial  "  R  Salt "  (^-naphthol- 

3.6-disodium-disulphonate)  are  dissolved  in  water  and  made  up  to  1  litre 

N.N 
to  give  an  approximately      solution.    A  ^  phenyldiazonium  solution 

is  prepared  and  100  c.cs.  of  it  poured  into  a  100-c.c.  measuring 
cjdinder  which  had  been  previously  cooled  in  an  ice  chest.  The  cylinder 
is  then  immersed  in  a  vessel  containing  ice-water.  50  c.cs.  of  the  R  salt 
solution  are  measured  out  into  a  beaker,  8  gms.  sodium  carbonate  added, 
and  stirred  to  dissolve.  15  c.cs.  of  the  phenyldiazonium  solution  are  then 
added  from  the  measuring  cylinder.  A  red  dye  is  formed  which  is  thrown 
out  of  solution  by  the  addition  of  common  salt.  After  adding  sufficient 
salt,  a  drop  "  spotted  "  on  filter  paper  leaves  a  sediment  of  dye  in  the  centre, 
and  the  outspread  is  colourless.  A  small  quantity  of  diazonium  solution 
from  the  stock  solution  is  poured  into  a  small  beaker  to  be  used  for  testing. 
If  the  outspread  on  filter  paper  of  a  drop  from  the  solution  containing  the 
dye  is  touched  with  a  glass  rod  dipped  in  the  diazonium  test  solution,  a 
red  dye  is  formed,  provided  a  sufficient  quantity  of  diazonium  solution  has 
not  been  added  already — which  is  not  intended.  Proceeding  in  this  way, 
and  testing  after  each  addition,  small  quantities  of  diazonium  solution 
from  the  measuring  cylinder  are  added  until  a  drop  tested  on  filter  paper 
no  longer  forms  a  red  dye. 

Since  1  mol.  of  R  salt  couples  with  1  mol.  of  diazo  compound,  the 
strength  of  the  R  salt  solution  can  be  easily  calculated,  and  hence  the 

N 

quantity  of  water  which  must  be  added  to  make  it 

Standard  "  R  salt  "  is  used  for  estimating  amines  (p.  490). 


Estimation  of  Amines. 

(a)  By  Diazotisation. — Many  amines  which  diazotise  readily  can  be 
accurately  estimated  with  standard  nitrite.  The  principle  of  the 
method  is  exactly  the  same  as  that  underlying  the  standardisation  of 
sodium  nitrite  with  sulphanilic  acid,  benzidine  or  aniline.  As  a  general 
rule  1/100  mol.  wt.  of  the  amine  is  dissolved  along  with  rather  more  than 
three  times  its  acid  equivalent  of  hydrochloric  acid  in  water  ;  the  solution 

N 

is  cooled  to  0°  by  the  addition  of  ice,  and  -~  sodium  nitrite  solution  is  run 


490  SYSTEMATIC  ORGANIC  CHEMISTRY 


in  until  an  end  point  is  indicated  by  starch-iodide  paper  (see  preparation 
of  standard  sodium  nitrite). 

N 

%  purity  =  c.cs.  of  ^-  nitrite  X  5. 

Certain  diazonium  salts  such  as  those  of  the  nitranilines  and  chloranilines 
decompose  starch  iodide  in  the  same  way  as  free  nitrous  acid  ;  such  com- 
pounds should  be  estimated  by  coupling  (Method  (b)  ). 

(b)  By  Diazotiwtion  and  Coupling. — Exactly  tJq  mol.  wt.  of  the  amine 

is  diazotised  as  described  under  (a).    8  gms.  sodium  carbonate  are  added 

to  the  diazotised  solution  and  stirred  until  dissolved.    The  solution  is 

diluted  and  cooled,  so  that  its  strength  is  equivalent  to  about  1%  amino 

N  .  . 

and  its  temperature  about  5°.    ^  R  salt  solution  is  then  run  in  until  an 

excess  of  diazo  solution  no  longer  appears  on  spotting  on  filter  paper  (see 
p.  489),  the  dye  being  first  salted  out  by  the  addition  of  common  salt.  By 
the  above  method,  two  values  are  obtained — a  "  nitrite  "  value,  and  an 
"  R  salt  "  value,  and  these  should  agree. 

The  above  outline  is  general,  but  is  subject  to  variation  for  the  par- 
ticular amine  under  estimation.  For  instance,  the  amount  of  sodium  car- 
bonate— the  essential  point  is  to  have  the  mixture  alkaline  during  the 
coupling — depends  on  the  acidity  of  the  diazonium  solution,  and  the 
presence  of  acid  groups,  such  as  sulphonic.  When  the  coupling  is  carried, 
out  in  acetic  acid  solution,  sodium  acetate  is  added  in  place  of  sodium 
carbonate  and  in  three  times  the  quantity. 

Estimation  of  Phenolic  Compounds. 

Phenolic  compounds  which  couple  readily  and  completely,  with 
diazonium  compounds,  can  be  estimated  by  titration  with  a  standard 
diazonium  solution.  The  standardisation  of  R  salt  affords  one  example 
of  the  method. 

Example. — /?-Naphthol. — 1'44  gms.  (TJ^  mol.)  of  ^-naphthol  are  dissolved 
in  4  c.cs.  caustic  soda  solution  (15%) ;  to  this  is  added  100  c.cs.  water  and 
3  gms.  of  solid  sodium  carbonate.    The  whole  is  then  made  up  to  200  c.cs. 

N 

in  a  flask.    50  c.cs.  of  this  are  placed  in  a  beaker,  and  ice-cold  ^  phenyl- 

diazonium  solution  run  in  until  a  drop  on  filter  paper  no  longer  shows  an 
excess  of  /?-naphthol  when  tested  with  diazonium  solution.  (For  end 
point  see  R  salt,  p.  489.) 

%  purity  =  c.cs.  of  diazonium  solution  X  2. 

Estimation  of  H  Acid  (Acid  Sodium  Salt). 

(a)  By  Diazotisation. — 3-41  gms.  (tJq  mol.)  are  dissolved  in  5  c.cs. 
of  10%  sodium  carbonate  solution  and  diluted  to  250  c.cs.    25  c.cs.  of 


ESTIMATIONS  BASED  ON  DIAZOTISATION  OR  COUPLING  491 

cone,  hydrochloric  acid  are  then  added,  and  the  solution  diazotised  at  5° 
N 

with  w  sodium  nitrite. 

Li 

%  of  H  acid  =  c.cs.  of  nitrite  X  5. 

(b)  By  Coupling. — 3-41  gms.  H  acid  are  dissolved  in  50  c.cs.  of  10% 

N 

sodium  carbonate  and  diluted  to  300  c.cs.        phenyl diazonium  solution 

is  then  added  until  the  end  point  is  obtained  as  determined  by 
"  spotting  ?'  (see  p.  489). 

o/    f  Ti        —  c"cs*  °^  diazonium  solution. 
/q  oi  1 1  acid  —  

For  a  good  quality  of  H  acid,  the  percentage  determined  by  diazotisa- 
tion  should  only  be  slightly  higher  than  that  determined  by  coupling. 


CHAPTER  XLII 


MISCELLANEOUS  ESTIMATIONS 

Estimation  of  ^-Phenylenediamine. 

The  para- diamines  cannot  be  estimated  by  means  of  the  diazo  reaction. 
The  following  estimation  is  based  on  the  formation  of  benzoquinone 
dichloro-imide  when  j9-phenylenediamine  in  hydrochloric  acid  solution  is 
added  to  a  solution  containing  excess  of  sodium  hypochlorite  and  sodium 
carbonate. 

A  solution  of  sodium  hypochlorite  is  prepared  by  diluting  50  c.cs. 
of  a  commercial  solution  containing  about  12 — -15%  available  chlorine, 
to  1000  c.cs.  Or,  a  corresponding  solution  may  be  prepared  by  passing 
chlorine  into  caustic  soda  (p.  508).   50  c.cs.  of  this  solution  are  titrated 

.  '  N 

with      sodium  arsenite  solution,  using  starch-iodide  paper  as  indicator. 

100  c.cs.  of  hypochlorite  solution  are  then  measured  out,  diluted  with  an 
equal  volume  of  cold  water,  and  about  1  gm.  of  solid  sodium  carbonate 
added.  10  c.cs.  of  the  solution  to  be  determined,  containing  2 — 6%  of 
^-phenylenediamine  dissolved  in  slight  excess  of  hydrochloric  acid,  is 
added  slowly  with  stirring.  The  mixture  should  then  give  a  strong 
reaction  with  starch-iodide  paper,  otherwise  the  experiment  must  be 
repeated,  using  either  less  diamine  or  more  sodium  hypochlorite  solution. 
On  the  addition  of  the  diamine  solution,  the  dichloro-imide  is  rapidly 
precipitated  as  an  almost  colourless  solid. 

C6H4(NH2)2  +  3C12  ->  C6H4 :  (NCl)a  +  4HC1. 

.     N  ' 

The  turbid  solution  is  then  titrated,  without  nitration,  with  sodium 

arsenite  solution,  using  starch- iodide  paper  as  external  indicator,  the  end 
point  being  sharply  defined  by  the  disappearance  of  the  blue  colour  on 
spotting.  At  the  end  of  the  titration  the  solution  should  be  alkaline, 
since  the  dichloro-imide  in  alkaline  solution  has  no  action  on  the  test- 

N 

paper.    The  difference  in  the  volume  of  the  ^  arsenite  solution  required 

for  the  titration  of  the  sodium  hypochlorite  itself  and  for  the  titration  of 
the  hypochlorite  plus  diamine  is  equivalent  to  the  amount  of  active  chlorine 
removed  from  the  solution  as  benzoquinone  dichloro-imide,  each  c.c. 
N 

of  |-  arsenite  solution  corresponding  to  0-0018  gm.  of  diamine. 

The  method  gives  good  results,  the  error  varying  from  0*3 — 0-7%. 
(J.  S.  C.  I.,  38,  408.) 

492 


MISCELLANEOUS  ESTIMATIONS 


493 


Estimation  of  Thiophen  in  Benzene. 

2  c.cs.  of  commercial  benzene  and  20  c.cs.  of  Denige's  reagent  (see  below), 
are  introduced  into  a  strong  test-tube  (2  cms.  X  15  cms.),  which  is  after- 
wards closed  with  a  good  wet  cork,  and  placed  in  a  shaking  machine  for 
3  hours.  (Even  without  shaking,  the  reaction  takes  place  to  some  extent.) 
At  the  end  of  this  time,  the  precipitate  is  collected  in  a  weighed  Gooch 
crucible,  washed  with  hot  water  until  neutral  to  litmus,  dried  at 
110°— 115°  C.  until  constant,  and  weighed  as  2(H9O.H9S04)C4H4S.  The 
weight  of  the  precipitate  X  0-0757  gives  the  weight  of  thiophen. 

To  prepare  the  above  reagent,  20  c.cs.  of  pure  cone,  sulphuric  acid  are 
poured  into  100  c.cs.  distilled  water,  5  gms.  of  finely  powdered  mercuric 
oxide  are  added  and  the  mixture  stirred  until  almost  all  dissolves.  The 
solution  is  then  filtered  and  the  nitrate  preserved  in  a  stoppered  bottle. 

The  Gooch  crucible  is  prepared  with  a  filtering  layer  of  good  fibrous 
asbestos  on  top  of  which  is  placed  a  perforated  porcelain  plate.  The 
asbestos  should  be  previously  purified  by  boiling  up  first  with  aqua  regia 
for  a  short  time,  and  then  with  cone,  hydrochloric  acid  for  a  week,  the  acid 
being  renewed  each  day.    (J.  S.  C.  I.,  38,  189.) 

Estimation  of  Enol  Modification  in  a  Compound  exhibiting 
Keto-enol  Tautomerism. 

The  enolic  form  reacts  instantly  with  an  alcoholic  solution  of  bromine, 
and  the  amount  of  bromine  used  corresponds  with  the  formation  of  a 
dibromide,  which  body,  however,  cannot  be  isolated  since  it  decomposes 
as  soon  as  formed  into  hydrogen  bromide  and  a  bromo-ketone. 

— C.OH  — C.Br.OH  —  C:0 

||         ->        |  ->        |  +  HBr. 

— CH  — CH.Br  —C.H.Br 

The  amount  of  enolic  compound  can  be  estimated  by  adding  a  standard 
solution  of  bromine  in  alcohol,  until  the  yellow  colour  just  persists,  but  the 
method  has  the  disadvantage  that  such  a  solution  of  bromine  is  unstable. 

In  the  following  method  a  slight  excess  of  an  alcoholic  solution  of 
bromine  is  added  to  an  alcoholic  solution  of  the  tautomeric  compound ; 
the  excess  of  bromine  is  immediately  removed  by  the  addition  of  a  few 
drops  of  alcoholic  ^-naphthol  solution  ;  potassium  iodide  solution  is  next 
added,  and  the  hydrogen  iodide  formed  by  interaction  with  the  hydrogen 
bromide  present  reduces  the  bromo-ketone  with  liberation  of  free  iodine 
which  is  estimated  by  titration  with  standard  thiosulphate  (in  absence  of 
starch).  As  one  molecule  of  iodine  is  equivalent  to  one  molecule  of  enolic 
compound,  the  percentage  of  this  form  is  easily  calculated. 

—CO         2HI  —CO 

I   >        I       +  I2  +  HBr. 

— C.HBr  — CH2 

Example. — Ethyl  Aceto-acetate. — The  following  reagents  are  prepared : — 
N 

1.  An  approximately       alcoholic  bromine  solution;   the  bromine 


494  SYSTEMATIC  ORGANIC  CHEMISTRY 


itself  being  previously  purified  by  shaking  up  with  sulphuric  acid,  then 
separating  and  distilling. 

2.  A  10%  solution  of  potassium  iodide. 

N 

3.  yq  sodium  thiosulphate  solution. 

4.  1  gm.  of  ^-naphthol  dissolved  in  20  c.cs.  alcohol. 

1-625  gms.  ester  are  dissolved  in  100  c.cs.  alcohol  in  a  flask,  and  cooled  to 
—  7°.  The  contents  are  given  a  swirling  motion,  and  ice-cold  bromine 
solution  (21  c.cs.)  added  until  a  faint  yellow  colour  is  produced.  Alco- 
holic /?-naphthol  sufficient  to  remove  colour  is  then  added.  The  time 
for  the  addition  of  bromine  and  /?-naphthol  should  not  exceed  20  seconds. 
5  c.cs.  of  the  potassium  iodide  solution  are  added,  and  the  contents 
N 

titrated  with  —  thiosulphate.   Volume  of  thiosulphate  =  18*7  c.cs.  which 

is  equivalent  to  18-7  X  0-0127  gm.  iodine,  or  to  18-7  X  0-0065  gm.  enolic 
ester 

o/  T7    i      100  X  18-7  X  0-0065     _  ,n 
-•-  %  Enol  =  ^  =  749. 

Estimation  of  Anthracene  in  Commercial  Anthracene. 

The  estimation  of  anthracene  depends  on  its  oxidation  by  means  of 
chromic  acid  to  anthraquinone. 

1  gm.  of  the  sample  is  dissolved  in  45  gms.  of  glacial  acetic  acid  by 
heating  on  a  sand  bath  under  a  long  reflux  condenser.  When  the  contents 
of  the  flask  are  boiling,  15  gms.  of  crystallised  chromic  acid  dissolved  in 
50%  acetic  acid  are  very  gradually  added  (2  hours).  When  the  addition  of 
chromic  acid  is  complete,  the  mixture  is  boiled  for  another  2  hours.  After 
cooling,  the  contents  are  treated  with  400  c.cs.  water,  and  the  precipitated 
anthraquinone  filtered  off,  washed  with  cold  water,  then  with  boiling 
dilute  alkali  and  finally  with  boiling  water,  until  the  washings  are  free 
from  alkali.  The  residue  is  then  washed  into  a  small  porcelain  basin  and 
dried  at  100°.  10  gms.  of  Nordhausen  sulphuric  acid  (about  5%  S03)  are 
added,  and  the  mixture  heated  for  10  minutes  at  100°.  After  cooling, 
it  is  carefully  poured  (caution  !)  into  200  c.cs.  of  cold  water,  the  anthra- 
quinone filtered,  washed  with  dilute  alkali,  and  finally  with  water  as 
before.  It  is  then  dried  and  weighed.  The  anthraquinone  is  volatilised 
by  heating  on  a  sand  bath  and  the  residue  is  weighed.  The  difference 
gives  the  weight  of  anthraquinone. 

178 

Wt.  of  anthraquinone  X        =  weight  of  anthracene. 

Estimation  of  Acetone. 

1.  Volumetrically. — Iodine  in  alkaline  solution  reacts  with  acetone  to 
give  iodoform,  a  reaction  which  is  used  in  the  estimation  of  the  ketone. 

1  mol.  acetone  =  3  mols.  iodine. 

CH3COCH3  +  3KIO  ->  CH3COCI3  +  3KOH 
CH3COCI3  +  KOH  ->  CHI3  +  CH3COOK. 


MISCELLANEOUS  ESTIMATIONS 


495 


The  excess  of  iodine  may  be  decomposed  as  follows  : — 

I2  +  2K0H  -  KIO  +  KI  +  H20 
KIO  +  KI  +  2HC1  =  I2  +  2KC1  +  H20 

and  is  titrated  with  thiosulphate  solution. 

A  weighed  quantity  (about  2  c.cs.)  of  acetone  is  made  up  to  500  c.cs. 
with  water.    15  c.cs.  of  this  solution  are  shaken  with  50  c.cs.  of  approx- 
imately normal  caustic  potash  in  a  250-c.c.  stoppered  flask.  About 
N 

100  c.cs.  of  ^  iodine  solution  are  then  run  in  from  a  burette,  and  the 

mixture  shaken  for  10  minutes.    It  is  then  acidified  with  about  50  c.cs. 

of  approximately  normal  sulphuric  acid.    The  excess  of  iodine  which  is 

...  N 
thereby  liberated  is  titrated  with  ^  thiosulphate  ;  this  amount  deducted 

from  the  quantity  of  iodine  originally  added  gives  the  amount  of  iodine 
used. 

N 

1  c.c.  of      iodine  =  0-000968  gm.  acetone. 

Example. — 

Weight  of  acetone  =2-0  gms. 
Volume  of  acetone  solution  =  15  c.cs. 
N 

iodine  added  =82-5  c.cs. 

N 

„       —  thiosulphate  =  21*0  c.cs. 
N  . 

iodine  used  up  =  61-5  c.cs. 

Wt.  of  acetone  in  15  c.cs.  solution     =  61-5  X  0-000968  gms. 

,    ,            61-5  X  0-000968  X  500 
,,       500  c.cs.  solution     —  ^  gms. 

n/   .  61-5  X  0-000968  X  500  X  10 

.-.  %  Acetone  =  15  2 

=  99-38. 

2.  Gravimetricatty. — Mercuric  sulphate  combines  with  aliphatic  ketones 
to  give  insoluble  precipitates  which,  when  dried  in  vacuo,  have  the  general 
formula  (2HgS04.3HgO).4COK2.  These  compounds  have  such  high 
molecular  weights  that  very  small  quantities  of  the  ketone  need  be  used. 

5  gms.  of  mercuric  oxide  are  dissolved  in  120  c.cs.  of  cold  30%  sulphuric 
acid.  25  c.cs.  of  this  solution  and  25  c.cs.  of  the  acetone  solution  con- 
taining about  0-05  gm.  of  acetone,  are  placed  in  a  strong  glass  bottle  of 
about  200  c.cs.  capacity.  The  glass  stopper  is  wired  in,  and  the  bottle 
heated  to  100°  on  a  water  bath  for  10  minutes.  When  cold,  the  whole  is 
filtered  through  a  weighed  filter  paper,  and  the  residue  washed  with  cold 
water,  dried  in  vacuo  for  12  hours  and  weighed. 

Wt.  of  acetone  ==  weight  of  precipitate  X  0-0584. 


496 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Example. — 

Wt.  of  acetone  in  25  c.cs.  of  water  =  0-052  gm. 

„       precipitate  =  0-886  „ 

.%    „       acetone  =  0-886  X  -0584 

=  0-0517  gm. 

0-0517  X  100 
•'•  %  acetone  =  

=  99-4 

Estimation  of  Glucose  or  Cane  Sugar  in  Solution  by  means  of 
Fehling's  Solution. 

Fehling's  Solution  consists  of  two  parts.  The  first,  a  solution  of 
69-28  gms.  of  pure  crystalline  copper  sulphate  dissolved  in  water  with 
the  addition  of  1  c.c.  of  pure  sulphuric  acid,  and  the  whole  made  up  to 
1  litre  ;  the  second,  a  solution  of  350  gms.  of  Rochelle  salt  (sodium 
potassium  tartrate)  and  120  gms.  of  sodium  hydroxide  (purified  from 
alcohol)  dissolved  in  water  and  made  up  to  1  litre.  Equal  volumes  of 
these  two  parts  are  mixed  just  before  use.  Each  c.c.  of  the  resulting 
solution  is  equivalent  to  0-005  gm.  glucose  or  to  0-00475  gm.  cane  sugar. 
The  solution  deteriorates  after  a  time,  and  should  be  standardised 
frequently  against  pure  glucose  or  pure  cane  sugar. 

Standardisation. — Some  pure  glucose  is  dried  for  12  hours  in  a  vacuum 
desiccator  over  sulphuric  acid  and  a  solution  of  known  concentration 
(0-5—1%)  made. 

5  c.cs.  of  each  part  of  the  Fehling's  solution  are  measured  out  into  a 
porcelain  dish,  diluted  with  40  c.cs.  of  dilute  caustic  soda  solution,  and 
gently  boiled.  Glucose  solution,  about  1  c.c.  at  a  time,  is  then  run  from 
a  burette,  and  the  mixture  boiled  after  each  addition  until  the  blue  colour 
is  finally  discharged. 

The  titration  is  then  repeated,  all  but  2  c.cs.  of  the  volume  of  glucose 
solution  used  in  the  first  determination  being  run  in  at  once,  and  the 
remainder  in  drops  until  the  blue  colour  just  vanishes.  The  end  point 
is  more  easily  observed  when  the  dish  is  slightly  tilted.  Several  deter- 
minations are  made  until  concordant  results  are  obtained.  If  the  end 
point  is  indistinct,  a  dilute  acetic  acid  solution  of  potassium  ferrocyanide 
"  spotted  "  on  a  white  plate  may  be  used  as  external  indicator.  A  brown 
coloration  is  observed  so  long  as  copper  is  present  in  solution. 

Alternately  the  standardisation  may  be  carried  out  with  a  solution  of 
"  invert  sugar  "  prepared  by  heating  4-75  gms.  of  cane  sugar  with  50  c.cs. 
of  2%  hydrochloric  acid  to  boiling  for  10  to  15  minutes,  then  cooling, 
neutralising  exactly  with  sodium  carbonate,  and  diluting  to  1  litre. 

Estimation  of  Glucose  or  Cane  Sugar  in  Solution. — The  estimation  of 
glucose  or  inverted  cane  sugar  solution  is  carried  out  similarly  to  the  fore- 
going standardisations.  The  concentration  must  be  of  the  order  of  0-5 — 
1%,  otherwise  reliable  results  are  not  obtained.  As  cane  sugar  does  not 
reduce  Fehling's  solution  until  inverted,  a  mixture  of  cane  sugar  and' 
glucose  may  be  estimated  by  determining  the  glucose  prior  to  inversion, 


MISCELLANEOUS  ESTIMATIONS 


497 


and  then  the  total  glucose  and  fructose  after  inversion.  Fructose,  galac- 
tose, mannose,  maltose,  lactose,  may  be  estimated  similarly,  but  the 
results  are  not  satisfactory  in  all  cases. 

Instead,  of  measuring  the  volume  of  the  Fehling's  solution,  the  hot 
solution  of  sugar  may  be  mixed  with  an  excess  of  Fehling's  solution, 
heated  in  a  boiling  water  bath  for  15  minutes,  and  the  precipitated 
cuprous  oxide  estimated  in  either  of  the  following  ways  : — 

1.  By  filtration  through  a  weighed  "  asbestos "  Grooch  crucible, 
washing  first  with  hot  water,  then  with  alcohol,  and  finally  with  ether, 
and  drying  for  30  minutes  in  a  steam  oven. 

2.  By  filtration  (as  in  1.),  washing  with  hot  water,  then  dissolving 

N 

the  Cu20  in  a  known  volume  of      permanganate  solution  previously 

diluted  with  4  times  its  volume  of  25%  sulphuric  acid,  and  titrating  the 

N 

excess  of  permanganate  at  40° — 50°  with  an      solution  of  oxalic  acid. 
N 

1  c.c.  of  -pr  permanganate  is  equivalent  to  0-01426  gm.  cuprous  oxide, 

or  to  0-01426  x  0'5045  gm.  glucose  or  to  0*01426  X  0-4793  gm.  cane 
sugar.    (J.  S.  C.  L,  16,  981.) 


PART  IV 


CHAPTER  XLIII 

INORGANIC  SECTION 

Reagents. 

Sulphuric  Acid.— The  acid  used  in  the  laboratory  is  the  commercial, 
96—98%  acid.  The  100%  acid  (monohydrate)  can  be  made  from  this 
by  adding  the  requisite  amount  of  oleum  (see  p.  306).  Usual  impurities  : 
lead  sulphate  and  oxides  of  nitrogen. 

Oleum. — Oleum  is  supplied  in  all  strengths  up  to  70%  free  S03. 
From  0—40%  free  S03  it  is  liquid  ;  from  40—60%  free  S03,  it  is  solid ; 
from  60—70%  free  S03  it  is  liquid  ;  above  70%  it  is  solid.  The  acid 
should  be  kept  in  well  stoppered,  stout  glass  bottles,  and  when  it  is 
necessary  to  melt  the  acid,  the  stopper  is  withdrawn,  a  watch-glass  placed 
on  the  mouth  of  the  bottle,  and  the  bottle,  while  placed  on  a  layer  of  sand 
in  a  large  vessel,  is  warmed  with  a  small  flame.  The  bottle  is  then  fitted 
with  a  wash-bottle  attachment,  and  any  desired  quantity  of  oleum  is  forced 
out  by  gentle  air  pressure  from  hand  or  foot  bellows  (the  mouth  must  not 
be  used).  For  the  preparation  of  oleums  of  definite  strengths,  see  p.  306. 
Usual  impurities  :  ferric  sulphate,  sulphur  dioxide  and  lead  sulphate.  For 
estimation,  see  p.  305. 

Hydrochloric  Acid. — The  pure  concentrated  aqueous  acid  contains 
about  38%  HOI.  The  commercial  acid  containing  about  30%  HC1  serves 
for  most  organic  preparations.  The  yellow  colour  is  due  to  iron.  Usual 
impurities  :  chlorine,  sulphuric  acid  and  iron. 

Hydriodic  Acid.— Both  the  cone,  acid  and  the  acid  of  constant  boiling 
point  (D.  1-7,  57%  HI)  (see  p.  502)  are  on  the  market.  Usual  impurity : 
iodine. 

Nitric  Acid. — The  commercial  cone,  acid  generally  contains  about 
70%  HN03.  Fuming  nitric  acid  (see  p.  508)  containing  about  95%  HN03 
(D.  1-5)  is  available  commercially.  Usual  impurities  :  oxides  of  nitrogen, 
sulphuric  acid,  hydrochloric  acid,  chlorine  and  iodine. 

Phosphoric  Acid.— The  commercial  acid  (D.  1*5)  contains  65%  H3P04  ; 
syrupy  phosphoric  acid  contains  about  90%  H3P04.  Usual  impurities  : 
sulphuric  acid  and  iron. 

Anhydrous  Aluminium  Chloride. — It  is  best  to  buy  this  reagent  from 
a  reliable  manufacturer.  As  a  high  pressure  frequently  exists  in  bottles 
containing  this  reagent,  such  bottles  should  be  opened  with  care,  a  cloth 
being  wrapped  round  the  bottle  during  the  operation.    If  the  commercial 

498 


INORGANIC  SECTION 


499 


product  is  not  available,  it  may  be  prepared  (see  p.  503).  Usual  impurity  : 
water. 

Titanous  chloride  comes  on  the  market  in  the  form  of  a  20%  solu- 
tion (see  p.  482).  Usual  impurities  :  oxidation  products.  For  the  many 
reducing  reactions  in  which  titanous  chloride  is  used  it  may  be  replaced 
by  titanous  sulphate,  which  must  be  used  when  there  is  danger  of 
chlorination. 

Copper  Bronze  (Kahlbaum,  "  Natur  Kupfer  "). — This  product  can  be 
used  for  the  Gattermann  reaction  (p.  150)  in  place  of  copper  powder 
(p.  504).  The  bronze  should  be  washed  with  ether  to  remove  oil  and 
grease. 

Zinc-Dust. — Commercial  varieties  vary  much  in  character  and  are 
subject  to  deterioration  ;  they  contain  usually  90 — 95%  Zn  (for  estima- 
tion, see  p.  506)  ;  they  should  be  preserved  in  an  airtight  vessel  and 
should  be  occasionally  estimated.  Two  other  forms  of  zinc  for  reducing 
purposes  are  on  the  market — a  ground  zinc,  made  by  grinding  metallic  zinc, 
and  a  variety  in  the  form  of  powder  containing  2%  of  lead,  which  gives 
specially  good  results.    Usual  impurities  :  zinc  oxide,  iron  and  arsenic. 

Caustic  Soda. — This  is  supplied  in  powder,  flake  and  stick  forms,  the 
former  two  being  more  convenient  to  use.  The  pure  variety  comes  on 
the  market  in  the  form  of  sticks.  In  weighing  out  a  quantity,  the  sticks 
should  not  be  handled.  Pieces  of  a  desired  size  can  be  broken  of!  by 
elevating  one  end  and  dealing  a  sharp  blow  with  a  knife  or  file  at  the 
desired  point.  The  same  remark  applies  to  caustic  potash  sticks. 
30 — 40%  solutions  of  caustic  soda  are  available  in  commerce.  Usual 
impurities  :  sodium  chloride  and  sodium  carbonate. 

Ammonia.— A  solution,  D.  0*88,  containing  35%  NH3  comes  on  the 
market.    Cylinders  of  anhydrous  liquid  ammonia  are  also  available. 

Sodium  Nitrite. — The  commercial  product  contains  97—98%  NaN02, 
and  is  suitable  for  most  organic  reactions.  For  estimation  see  p.  487. 
Usual  impurity  :  sodium  nitrate. 

Sodium  Sulphide  (Na2S,9H20). — The  commercial  variety  consists  of 
dirty  brown  deliquescent  crystals.  It  can  be  used  for  most  purposes. 
Usual  impurities  :  poly  sulphides  and  sulphate.   For  estimation  see  p.  508. 

Sodium  Bisulphite  (see  p.  506). — This  is  available  in  the  solid  form, 
and  as  a  30%  solution  commercially.  The  product  as  prepared  on  p.  506 
is  the  most  reactive  in  many  cases.    Usual  impurity :  bisulphate. 

Sodium  Hypochlorite  (see  p.  508).— The  commercial  solution  (about 
30%)  is  available.  Usual  impurities  :  caustic  soda,  sodium  chloride  and 
sodium  chlorate. 

Iron  Filings  and  Iron  Powder. — These  are  recommended  for  many 
operations  in  place  of  zinc  and  tin,  on  account  of  cheapness.  Usual 
impurities :  oxides. 

Stannous  Chloride.— The  product  should  be  obtained  from  a  reliable 
.firm.  It  should  be  frequently  estimated,  as  it  deteriorates  through 
oxidation. 

Tables  of  the  gravities  and  strengths  of  some  reagents  are  given  on 
pp.  500,  509-511. 

K  K  2 


500  SYSTEMATIC  ORGANIC  CHEMISTRY 


It  is  important  that  the  common  bench  reagents  should  be  of  a  definite 
strength.  The  following  table  shows  the  approximate  strengths  of  the 
ordinary  bench  reagents,  which  have  been  found  convenient  in  practice  : — 


Approximate  Concentration  of  Reagents. 


Beagent. 

D. 

Approx. 

Nor- 
mality. 

1  litre 
1ST  solution 
equivalent  to  c.c. 

100  gms. 
contain 

100  CCS 

contain 

1  -84. 

ou 

Q5»fi  cms 

1  75'Q  cms 

H2S04 

H2S04 

IT  SO  rlil 

XI  20U^  tXXX . 

I  10 

O 

900 

1  •  t\  rrm  a 

94.  ^  nrm  q 
Z/rt  0  gins. 

(11.+  6-4  1.  water). 

H2S04 

H2S04 

XlV_yl  cone. 

1  9 

1I1 

0  i  a  gms. 
ii\ji 

tt  0  gms. 

UP]  Hil 

XXVyl  1111. 

i  Uo 

K 
O 

900 

ID   O  glllb. 

1  8.9  frmc 
AO  £1  glllo. 

(1  ]    _l  l.U  waters 

HC1 

HC1 

TT1STO  oawo 

J.Ill  \J  ^  \J\JX.\.\J» 

1  -4 

D«7 

U«J  O  glXXUs 

Q  1  . 4  rem  a 
VI  rt  gXXXb. 

UNO 

XX 1\|  \J  3 

HN03  dil. 

1-17 

5 

200 

27-1  gms. 

31-5  gms. 

(11.  +2  1.  water). 

HNO3 

HNO3 

C2H402  cone. 

1-06 

18 

56-5 

100  gms. 
C2H402 

106  gms. 
C2H402 

C2H402  dil. 

1-04 

5 

203 

28  gms. 
C2H402 

29-5  gms. 
C2H402 

KOH 

1-19 

5 

195 

22  gms. 

28-8  gms. 

(280  gms.  in  1  1.). 

KOH 

KOH 

NaOH 

1-17 

5 

200 

15  gms. 

20  gms. 

(200  gms.  in  1  1.). 

NaOH 

NaOH 

NH4OH 

0-96 

5 

200 

9-5  gms. 

8-5  gms. 

(1 1.  strong  +  31.  water). 

NH3 

NH3 

Test  Papers  and  Solutions. 

1.  Litmus  Paper. — Used  as  an  indicator  for  all  weak  and  strong  acids 
and  bases.    Turned  red  by  acids  and  blue  by  alkalis. 

Cubes  of  best  quality  litmus  containing  50 — 90%  calcium  sulphate 
are  ground  and  washed  with  benzene,  then  with  alcohol.  4 — 5  gms.  of 
the  residue  are  then  dissolved  in  1  litre  of  water  ;  good  quality  filter  paper 
is  soaked  in  the  solution  and  dried  by  hanging  on  threads.  It  is  then 
cut  into  small  pieces. 

For  red  litmus  a  few  drops  of  acetic  acid  are  added  to  the  solution, 
and  for  blue  litmus,  ammonia  is  used. 

2.  Phenolphthalein  Paper. — Used  in  acidimetry  and  alkalimetry. 
Turned  red  by  alkalis,  reacting  with  ammonia  and  sodium  carbonate,  but 
not  with  bicarbonate.    Used  chiefly  in  analytical  work. 

0-5  gm.  of  phenolphthalein  is  dissolved  in  500  c.cs.  of  hot  water,  and 
filter  paper  is  soaked  in  the  hot  solution  and  dried. 

A  few  drops  of  a  very  dilute  alcoholic  solution  may  be  used  as  an  internal 
indicator. 


INORGANIC  SECTION 


3.  Congo  Paper.— Used  as  an  indicator  for  acids.  Turner 
by  mineral  acids  and  violet  by  strong  organic  acids. 

1  gm.  Congo  Red  is  dissolved  in  1  litre  of  water  to  which  a  fev 
of  ammonia  have  been  added.    Filter  paper  is  soaked  in  the  w 
solution  and  dried. 

4.  Brilliant  Yellow  Paper. — Used  as  an  indicator  for  alkalis.  Turned 
red  by  alkalis  and  by  alkali  carbonates  and  ammonia. 

1  gm.  of  the  dye  is  dissolved  in  1  litre  of  water  and  filter  paper  dipped 
in  the  solution  and  dried. 

The  alkali  salts  of  phenols  and  naphthols  also  give  an  alkaline  reaction, 
so  that  free  alkali  must  be  tested  for  in  the  following  way.  A  crystal  of 
ammonium  chloride  is  added  to  a  few  drops  of  the  solution  placed  on 
a  watch-glass,  and  the  latter  warmed  with  a  very  small  flame.  Another 
watch-glass  with  a  piece  of  moistened  red  litmus  paper  adhering  to  its 
concave  side,  is  placed  over  the  other  one,  and  if  the  liquid  is  alkaline  the 
litmus  paper  will  Be  turned  blue.  This  method  can  also  be  used  where 
the  colour  or  solubility  of  the  substance  to  be  tested  prohibits  the  direct 
use  of  test  papers. 

5.  Thiazole  Paper  (Mimosa  Paper). — Used  as  an  indicator  for  free 
alkali  and  is  preferable  to  turmeric.  Turned  red  by  alkalis,  but  not 
influenced  by  ammonia  even  in  high  concentrations. 

Prepared  similar  to  Congo  Red  paper,  the  dye  thiazole  yellow  (Clayton 
Yellow)  being  employed. 

6.  Starch-Iodide  Paper. — Used  as  an  indicator  for  nitrous  acid,  and 
for  halogens  and  other  oxidising  agents.  Turned  bluish  violet  by  a  trace 
of  oxidising  agent  and  brown  by  excess. 

10  gms.  of  pure  starch  are  ground  up  with  100  c.cs.  of  cold  water  and 
the  mixture  poured  slowly  into  2  litres  of  boiling  water  with  good  stirring. 
The  whole  is  boiled  for  a  few  minutes,  then  cooled  rapidly.  2  gms.  of 
potassium  iodide  are  added  and  1  gm.  of  cadmium  iodide.  When  all  is  in 
solution,  filter  paper  is  dipped  in  and  dried  in  an  atmosphere  free  from 
fumes. 

The  solution  does  not  keep  and  should  be  freshly  prepared. 

The  solution  may  be  used  as  an  indicator  by  "  spotting  "  on  filter  paper. 

When  the  paper  is  used,  a  drop  of  the  test  solution  is  removed  on  a  glass 
rod,  and  lightly  drawn  across  the  paper. 

The  papers  should  be  tested  each  time  they  are  used  by  treating  with  a 
1%  solution  of  hydrochloric  acid  containing  1  drop  of  normal  sodium 
nitrite  solution. 

7.  Lead  Acetate  Paper. — Used  for  detecting  H2S,  with  which  it  gives 
a  brown  coloration.  ^Filter  paper  is  soaked  in  a  solution  of  5  gms.  lead 
nitrate  or  acetate  or  ferrous  sulphate  per  litre,  and  dried  in  an  atmosphere 
free  from  H2S.  Ferrous  sulphate  paper  does  not  keep. 

8.  Methyl  Orange.— Used  as  an  internal  indicator  in  acidimetry  and 
alkalimetry.  Turned  red  with  acid  and  yellow  with  alkali.  Can  be  used 
in  the  presence  of  carbonates  to  detect  free  alkali.  Is  acted  upon  by 
bicarbonate. 

1  gm.  of  methyl  orange  is  dissolved  in  1  litre  of  water. 


,/STEMATIC  ORGANIC  CHEMISTRY 


ji  Red. — Used  as  an  internal  indicator  like  methyl  orange, 
_ore  sensitive. 
a.  of  methyl  red  is  dissolved  in  1  litre  of  water. 
<  ote. — All  test  papers  and  solutions  should  be  preserved  in  well 
.coppered  bottles. 

Inorganic  Preparations,  etc. 

Chlorine. — Manganese  dioxide  is  placed  in  a  flask  and  just  covered 
with  cone,  hydrochloric  acid.  On  heating,  a  regular  current  of  chlorine  is 
obtained  which  is  passed  through  water  and  through  cone,  sulphuric  acid. 
Chlorine  can  also  be  prepared  by  heating  a  mixture  of  cone,  hydrochloric 
acid  (5  parts)  with  ground  potassium  dichromate  (1  part).  Another  con- 
venient method,  which  does  not  necessitate  the  use  of  heat,  consists  in 
treating  good  bleaching  powder — cubes  consisting  of  bleaching  powder 
and  plaster  of  Paris  are  sold  for  this  purpose — with  4onc.  hydrochloric 
acid. 

Bromine. — When  nascent  bromine  is  required,  a  mixture  of  sodium 
bromide  and  bromate  is  added  to  the  solution  of  the  substance.  The 
quantity  of  sulphuric  acid  required  by  the  following  equation  is  then 
added. 

5NaBr  +  NaBr03  +  6H2S04  =  6NaHS04  +  3H20  +  6Br. 

For  most  purposes  commercial  bromine  is  used,  although  this  form 
sometimes  contains  as  much  as  10%  of  impurities,  the  chief  of  which  is 
bromoform.    It  may  be  purified  by  shaking  up  with  cone,  sulphuric  acid. 

Hydrochloric  Acid. — Gaseous  hydrochloric  acid  is  conveniently 
prepared  in  a  Kipp  apparatus  charged  with  fused  ammonium  chloride  in 
lumps,  and  cone,  sulphuric  acid. 

Another  convenient  method  is  to  run  cone,  commercial  hydrochloric 
acid  (about  30%  HC1)  into  cone,  sulphuric  acid  from  a  dropping  funnel 
contained  in  a  suction  flask  or  Woulff  bottle. 

Hydrobromic  Acid. — Sulphur  dioxide  is  passed  on  to  the  surface  of  a 
mixture  of  35  c.cs.  of  bromine  and  200  c.cs.  of  water  until  a  uniform  pale 
yellow  solution  remains,  which  is  distilled. 

S02  +  Br2  +  2H20  =  2HBr  +  H2S04. 

The  sulphuric  acid  remains  behind,  and  the  distillate  which  may  contain 
traces  of  sulphuric  acid  is  redistilled  over  barium  bromide. 

When  large  quantities  of  hydrobromic  acid  are  required,  it  is  advisable 
to  pass  sulphur  dioxide  into  a  mixture  of  crushed  ice  and  bromine  until  a 
uniform  pale  yellow  solution  is  obtained. 

Hydriodic  Acid. — 11  parts  by  weight  of  iodine  are  placed  in  a  small 
round-bottomed  flask,  and  1  part  of  yellow  phosphorus,  cut  into  small  pieces 
and  dried,  is  gradually  added.  The  addition  of  each  piece  causes  a  flash 
of  light  and  the  contents  of  the  flask  become  liquid.  When  all  the  phos- 
phorus has  been  added,  solid  phosphorus  tri-iodide  separates  on  cooling. 
The  product  is  treated  with  1J  parts  of  water  and,  when  gently  heated, 


INORGANIC  SECTION 


503 


evolves  hydrogen  iodide,  which  is  passed  over  some  red  phosphorus 
moistened  with  a  little  water  in  a  U-tube.  Heating  is  continued  until  the 
liquid  just  becomes  colourless  ;  otherwise,  if  heating  is  continued  further, 
phosphine  and  phosphonium  iodide  are  formed,  which  may  cause  explo- 
sion. If  a  solution  of  hydriodic  acid  is  required,  the  gas  is  led  through  an 
inverted  funnel  into  a  small  quantity  of  cold  water.  This  solution,  if 
dilute,  may  be  concentrated  by  distillation.  At  127°  a  solution  of  con- 
stant boiling  point  passes  over  containing  57%  of  hydrogen  iodide  and  of 
density  1-70. 

Ammonia. — Ammonia  gas  can  be  conveniently  obtained  by  gently 
heating  cone,  ammonium  hydroxide  solution  (D.  0-88)  which  contains 
35%  of  the  gas.  The  evolved  gas  is  dried  by  passing  it  over  quicklime  or 
soda-lime. 

A  very  convenient  method  consists  in  dropping  cone,  ammonia  solution 
on  to  solid  caustic  potash  or  soda  packed  in  a  drying  tower  or  in  a  flask. 
If  a  relatively  large  quantity  of  alkali  is  used  the  gas  evolved  is  dry. 

Zinc- Ammonium  Chloride. — This  compound  is  formed  by  passing  a 
current  of  dry  ammonia  gas  into  molten  zinc  chloride,  ZnCl2.2NH3.  It 
can  also  be  obtained  by  passing  the  gas  over  pulverised  anhydrous  zinc 
chloride.  This  compound  gives  up  ammonia  on  heating  and  is  used  in 
place  of  the  concentrated  solution  in  certain  reactions. 

Aluminium-Mercury  Couple. — -Aluminium  foil  is  cut  in  small  strips 
and  formed  into  rolls.  It  is  then  placed  in  a  saturated  solution  of  mercuric 
chloride.  After  about  a  minute  the  foil  becomes  coated  with  a  film  of 
metallic  mercury.  The  liquid  is  poured  off  and  the  couple  well  washed 
with  water,  then  alcohol,  and  finally  benzene.  It  is  then  ready  for  use. 
The  couple  should  always  be  freshly  prepared  when  required. 

Zinc-Copper  Couple. —  Granulated  zinc  is  treated  several  times  with  a 
2%  solution  of  copper  sulphate,  the  decolorised  solution  being  poured 
off  each  time.  The  couple  is  washed  first  with  water  and  then  with 
alcohol,  after  which  it  is  ready  for  use. 

Anhydrous  Aluminium  Chloride. — Aluminium  shavings  are  freed  from 
oil  by  boiling  with  alcohol,  and  then  dried  in  an  air  bath  at  120°.  These 
are  then  packed  in  a  thoroughly  dry,  hard  glass  tube,  and  kept  in  position 
by  asbestos  plugs.  To  one  end  of  the  tube  is  attached  a  drying  apparatus 
consisting  of  two  sulphuric  acid  wash-bottles.  To  the  other  end  is 
attached  a  receiving  apparatus  in  the  form  of  a  wide-mouthed  bottle, 
which  is  closed  with  a  cork  suitably  bored  to  admit  the  hard  glass  tube 
and  a  calcium  chloride  tube.  The  air  is  displaced  from  the  apparatus 
by  passing  a  stream  of  hydrochloric  acid  from  a  Kipp  apparatus  through 
the  drying  apparatus.  This  is  accomplished  when  the  gas  issuing  from 
the  calcium  chloride  tube  of  the  receiver  is  completely  soluble  in  water. 
The  hard  glass  tube  is  heated  in  a  small  furnace,  or  by  means  of  a  few 
Ramsay  burners,  the  heating  being  gradual  at  first,  and  commencing  at 
the  end  nearer  the  hydrochloric  acid  generator.  White  vapours  of 
aluminium  chloride  condense  in  the  receiver,  and  it  is  necessary  to  main- 
tain a  rapid  current  of  hydrochloric  acid.  The  reaction  is  finished  when 
there  is  only  a  small  dark  coloured  residue  of  aluminium  left  in  the  tube. 


504  SYSTEMATIC  ORGANIC  CHEMISTRY 


The  aluminium  chloride  should  be  preserved  in  well  stoppered  bottles 
(see  p.  498),  or  in  a  desiccator. 

Cuprous  Chloride.— 100  gms.  of  crystallised  copper  sulphate,  48  gms. 
common  salt  and  200  c.cs.  water  are  heated  to  boiling.  400  gms.  of  cone, 
hydrochloric  acid  and  72  gms.  of  copper  turnings  are  added,  and  the  whole 
is  gently  boiled  until  decolorised.  It  is  important  to  exclude  air  from 
the  flask,  which  may  be  done  by  using  a  plug  of  glass-wool  or  a  Bunsen 
valve.  The  solution  is  rapidly  decanted  from  unchanged  copper,  and 
then  distilled  water  added  until  no  more  cuprous  chloride  is  precipitated. 
The  precipitate  is  filtered  and  washed,  first  with  S02  solution,  and  then 
with  glacial  acetic  acid  until  the  filtrate  is  colourless.  It  is  removed 
from  the  filter  and  dried  on  a  water  bath  until  all  the  acetic  acid  is  driven 
off.    It  is  preserved  in  a  well  stoppered  bottle. 

For  the  Sandmeyer  reaction  it  is  not  necessary  to  isolate  the  solid 
product.  The  solution,  after  removing  the  copper,  is  treated  with  cone, 
hydrochloric  acid  until  the  total  weight  is  815  gms.  This  solution  contains 
about  10%  cuprous  chloride. 

Cuprous  chloride  can  also  be  made  by  bubbling  sulphur  dioxide  through 
a  strong  solution  of  cupric  chloride  and  filtering  off  the  white  precipitate 
of  the  desired  substance. 

Cuprous  Bromide. — 100  gms.  of  crystallised  copper  sulphate,  288  gms. 
potassium  bromide,  640  c.cs.  of  water,  160  gms.  of  copper  turnings,  and 
88  gms.  of  cone,  sulphuric  acid  are  boiled  until  the  whole  is  decolorised. 
The  solution  is  decanted  from  unchanged  copper. 

Lead  Peroxide. — 100  gms.  of  bleaching  powder  are  shaken  up  with 
1500  c.cs.  of  water  and  filtered.  The  filtrate  is  added  gradually  to  a  hot 
solution  of  50  gms.  lead  acetate  in  250  c.cs.  of  water  ;  the  addition  is 
continued  until  the  precipitate  turns  dark  brown,  and  until  no  precipitate 
is  formed  by  further  addition  of  bleaching  powder  solution  to  a  filtered 
test  portion.  The  liquid  is  decanted,  and  the  precipitate  washed  several 
times  with  water,  then  filtered  and  washed  with  water.  It  is  preserved 
in  a  well  stoppered  bottle  in  the  form  of  a  thick  paste. 

Evaluation. — 0*5  to  1  gm.  of  the  paste  is  treated  (with  cooling)  with 
hydrochloric  acid  (approximately  15%  solution).  The  chlorine  liberated 
on  heating  is  passed  into  a  solution  of  4  gms.  of  potassium  iodide  in  water, 

N 

and  the  iodine  liberated  is  titrated  with       sodium  thiosulphate.    1  c.c. 

of  this  thiosulphate  solution  is  equivalent  to  0-012  gm.  of  pure  lead 
peroxide. 

Copper  Powder. — 100  gms.  of  crystallised  copper  sulphate  are  dissolved 
in  350  gms.  of  water  in  a  beaker,  to  which  is  attached  a  mechanical 
agitator.  After  cooling  to  laboratory  temperature,  the  stirrer  is  set  in 
motion,  and  35  gms.  (or  more  if  necessary)  of  good  quality  zinc-dust  are 
gradually  added  until  the  solution  is  decolorised.  The  precipitated  copper 
is  washed  by  decantation  with  water.  Dilute  hydrochloric  acid  is  added 
to  the  precipitate  (to  remove  excess  zinc),  and  agitation  continued  until 
evolution  of  hydrogen  ceases.  The  powder  is  filtered  off  and  preserved 
in  a  moist  condition  in  a  stoppered  bottle. 


INORGANIC  SECTION 


505 


Sodium  Amalgam  —Weighing  of  Sodium. — A  lump  of  sodium  is  removed 
from  a  storage  bottle  and  the  surface  cleaned  with  a  knife.  The 
bright  lump  is  covered  with  petroleum  ether  (60° — 80°)  in  a  porcelain 
dish,  and  cut  into  small  pieces.  A  second  dish  (or  beaker)  containing 
petroleum  ether  is  weighed.  Small  lumps  of  sodium  are  removed  from 
the  first  dish,  quickly  dried  with  filter  paper,  and  added  to  the  second 
until  the  required  weight  of  sodium  is  obtained. 

Sodium  amalgam  is  usually  made  to  contain  2J%  of  sodium,  as  such  a 
product  is  solid  and  easily  pulverised. 

Pure  dry  mercury  is  placed  in  a  porcelain  mortar  and  warmed  in  an 
oven  to  60° — 70°.  It  is  then  removed  to  a  fume  cupboard,  and  the 
metallic  sodium,  removed  a  piece  at  a  time  from  the  petroleum  ether, 
quickly  dried  with  filter  paper,  and  plunged  under  the  surface  of  the 
mercury  with  a  pointed  glass  rod. 
The  hand  should  be  covered  with  a 
towel  during  the  operation.  When 
preparing  a  large  quantity  of  amalgam 
it  is  advisable  to  place  only  a  portion 
of  the  mercury  in  the  mortar  at  first, 
and  to  charge  this  with  sodium  before 
adding  another  portion  of  mercury  to 
the  contents.  Proceeding  in  this 
way  the  sodium  dissolves  quietly,  and 
there  is  practically  no  spluttering 
with  the  second  or  later  instalments 
of  mercury. 

The  usual  way  of  introducing 
sodium  into  a  liquid  is  in  the  form 
of  wire.  A  sketch  of  a  press  for  this 
purpose  is  shown  in  Fig.  78. 

Silver  Nitrite. — A  warm  concen- 
trated aqueous    solution   of  silver 

nitrate  containing  24  gms.  is  mixed  with  a  warm  concentrated  solution  of 
potassium  nitrite  containing  15  gms.  The  mixture  is  allowed  to  cool  and 
the  silver  nitrite  which  separates  filtered  off  and  rapidly  washed  with  water. 

Sodium  Ethylate  (or  Ethoxide). — 100  c.cs.  of  absolute  alcohol  are 
placed  in  a  flask  and  clean  metallic  sodium  in  small  strips  added  until 
it  no  longer  dissolves.  Gentle  heat  is  then  applied  to  effect  solution  of  the 
last  particle  of  metal:  The  excess  of  alcohol  is  then  distilled  off  up  to 
200°,  and  the  dry  residue  warmed  for  some  time  in  a  current  of  hydrogen. 
It  is  then  preserved  in  a  well  stoppered  bottle. 

It  is  not  always  necessary  to  isolate  the  dry  sodium  ethoxide,  the 
alcoholic  solution  being  sufficient  for  most  purposes. 

A  very  reactive  sodium  ethylate  can  be  obtained  by  adding  the  calcu- 
lated quantity  of  absolute  alcohol  diluted  with  2  vols,  of  dry  xylene 
to  granulated  sodium  under  xylene  (see  p.  506).  During  the  addition 
the  whole  is  well  cooled  and  shaken.  The  xylene  is  then  distilled  off  in  a 
current  of  dry  hydrogen. 


Fig.  78. 


506 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Granulated  Sodium. — 1  part  of  sodium  is  covered  with  10  parts  of  dry 
xylene  and  heated  to  120°.  The  flask  is  then  corked  and  wrapped  in  a 
thick  dry  cloth  and  well  shaken  for  a  short  time.  The  metal  is  thus 
obtained  in  the  form  of  a  powder.  No  more  than  20  gms.  of  sodium  should 
be  granulated  at  one  time.  A  dry  bucket  should  be  kept  at  hand  to  drop 
the  flask  into  in  case  of  breakage.  (B.,  21,  1464  ;  35,  3516 ;  J.  pr.  [2], 
54,  116.) 

Anhydrous  Sodium  Acetate. — Crystallised  sodium  acetate  (CH3.COONa. 

3H20)  is  heated  in  a  basin  over  a  small  flame.  The  salt  melts  and  for 
some  time  steam  is  evolved  until  all  the  water  of  crystallisation  is  driven 
off,  at  which  stage  the  mass  becomes  solid.  The  flame  is  then  increased, 
and  heating  continued  until  the  mass  melts  again.  Care  must  be  taken 
not  to  char  the  product  by  using  too  large  a  flame.  On  cooling,  the  mass 
solidifies  ;  it  is  broken  up  into  small  lumps  and  preserved  in  a  stoppered 
bottle. 

Anhydrous  Zinc  Chloride. — Crystallised  zinc  chloride  is  fused  in  a  porce- 
lain basin  for  a  short  time  until  no  more  steam  is  evolved,  then  cooled  and 
broken  up  into  small  pieces  which  are  preserved  in  a  well  stoppered  bottle. 

Sodium  Bisulphite. — Sodium  carbonate  is  covered  with  a  layer  of 
water — insufficient  to  dissolve  it — and  sulphur  dioxide  is  passed  into  the 
mixture.  After  a  time  the  solid  disappears  and  an  apple-green  solution 
remains  which  smells  strongly  of  sulphur  dioxide.  Sulphur  dioxide  may 
be  obtained  from  a  siphon  of  the  liquid  or  generated  by  the  action  of  cone, 
sulphuric  acid  on  sodium  sulphite. 

Sodium  bisulphite  solution  may  be  obtained  by  dissolving  the  sodium 
bisulphite  in  water,  but  the  solution  so  prepared  does  not  act  as  readily 
with  aldehydes  and  ketones  as  the  syrupy  apple-green  solution  described 
above. 

Sodamide. — This  is  prepared  by  the  action  of  ammonia  gas  on  sodium 
heated  to  300° — 400°.  For  the  preparation  of  quantities  of  20  gms.  or 
more  the  most  convenient  apparatus  consists  of  some  form  of  closed 
iron  pot  provided  with  inlet  and  outlet  tubes  for  ammonia.  The  appa- 
ratus, Fig.  36,  or  an  autoclave  from  which  any  copper  fittings  have  been 
removed  can  easily  be  adapted  to  suit  the  purpose.  If  the  apparatus  is 
free  from  rust,  the  sodium  may  be-  placed  directly  on  the  bottom  of  the 
pot.  Or,  it  may  be  contained  in  a  large  nickel  or  iron  crucible.  Before 
commencing  to  heat,  the  air  should  be  displaced  from  the  pot  by  am- 
monia, after  which  the  temperature  is  raised  to  and  maintained  at  300° — ■ 
400°  while  a  current  of  the  dry  gas  is  passed  over  the  molten  metal.  The 
reaction  takes  place  readily.  If,  after  cooling  and  opening  the  pot,  any 
soft  lumps  of  sodium  remain  on  the  surface,  these  can  be  picked  out  with 
a  knife,  or  else  the  apparatus  may  be  closed  again  and  more  ammonia 
passed  over  the  heated  metal.  The  sodamide  forms  a  hard  mass  which  is 
chipped  out  with  a  knife  or  chisel.  It  should  be  preserved  in  stoppered 
bottles. 

Evaluation  of  Zinc-Dust.— 0  5  gm.  of  zinc-dust  is  quickly  weighed 
out  and  placed  in  a  dry  250  c.cs.  graduated  flask  and  50  c.cs.  of  saturated 
solution  of  ferric  alum  added.    The  flask  is  stoppered  and  vigorously 


INORGANIC  SECTION 


507 


shaken  until  the  zinc-dust  disappears.  The  reaction  is  represented  by  the 
equation — 

Zn  +  Fe2(S04)3  =  ZnS04  +  2FeS04. 

25  c.cs.  of  cone,  sulphuric  acid  are  then  added  gradually,  cooling  being 
applied.    When  all  the  acid  is  added,  the  volume  is  made  up  to  250  c.cs. 
with  distilled  water.    50  c.cs.  of  this  solution  are  then  withdrawn  and 
N 

titrated  with  -permanganate, 
o 

N 

1  c.c.  j  KMn04  =  0  00654  gm.  Zn. 

Sulphur  Monochloride  (S2C12). — In  a  dry  retort  is  placed  100  gms.  of 
sulphur,  which  is  melted  by  gentle  heating.  The  retort  is  connected 
to  a  receiver  having  an  exit  tube.  Chlorine,  dried  by  passing  through 
cone,  sulphuric  acid  and  fused  calcium  chloride,  is  passed  into  the  melted 


Fig.  79. 


sulphur.  Sulphur  monochloride  distils  over,  and  the  passage  of  gas  is 
continued  until  very  little  sulphur  remains.  The  brownish  yellow  liquid 
which  collects  is  redistilled,  the  fraction  138° — 139°  being  collected,  and 
preserved  in  a  sealed  bottle. 

Phosphorus  Di-iodide  (PI2). — 5  parts  of  phosphorus  are  dissolved  in 
carbon  disulphide,  and  to  the  well  cooled  solution  41  parts  of  dry,  powdered 
iodine  are  added.  The  carbon  disulphide  is  then  distilled  off  from  the 
phosphorus  di-iodide. 

Phosphorus  Trisuiphide  (P2S3). — The  calculated  quantities  of  dry 
amorphous  phosphorus  and  sulphur  are  carefully  melted  together  in  a 
fireclay  crucible.    It  is  then  cooled  and  broken  up. 

Chlorosulphonic  Acid  (S03HC1). — A  mixture  of  common  salt  and  cone, 
hydrochloric  acid  is  placed  in  a  flask  and  hydrochloric  acid  gas  produced 
by  dropping  cone,  sulphuric  acid  on  to  it.  The  gas  is  dried  and  passed 
into  fuming  sulphuric  acid  in  a  retort  until  no  further  absorption 
takes  place,  cooling  being  applied  to  the  retort,  if  necessary.  The 
retort  is  then  heated  to  140° — 153°,  when  chlorosulphonic  acid  distils 
over.  A  pure  acid  can  be  obtained,  if  necessary,  by  a  further  distillation, 
the  fraction  boiling  at  149° — 151°  being  retained.    The  yield  is  nearly 


508 


SYSTEMATIC  ORGANIC  CHEMISTRY 


theoretical.  Fig.  79  shows  a  convenient  form  of  apparatus.  A  dilute 
chlorosulphonic  acid  can  be  readily  obtained  by  adding  common  salt  to 
fuming  sulphuric  acid. 

Fuming  Nitric  Acid. — This  can  be  prepared  by  distilling  2  mols.  sodium 
nitrate  with  1  mol.  cone,  sulphuric  acid  at  over  200°  ;  or  by  distilling  a 
mixture  of  strong  nitric  acid  and  cone,  sulphuric  acid.  The  addition  of 
3 — 5%  starch  is  effective.    Its  specific  gravity  at  15°  is  1-533. 

Sodium  Hypochlorite  (NaOCl). — 1.  Excess  of  sodium  carbonate  is 
added  to  a  solution  of  bleaching  powder.  The  filtrate,  after  removing 
the  CaC03,  contains  5%  available  chlorine,  and  the  solution  can  be  kept 
for  some  time. 

2.  Chlorine  gas  is  passed  into  a  cold  solution  of  caustic  soda  until 
nearly  all  the  soda  is  chlorinated.  The  solution  is  usually  made  to 
contain  10—15%  available  chlorine.    (J.  S.  C.  I.,  18,  1096.) 

Sodium  Hyposulphite  (Na2S204). — S02  is  passed  into  a  strong  solution 
of  NaHSOg  until  saturated,  and  the  mixture  reduced  with  zinc-dust. 

NaHS03  +  S02  +  Zn  =  ZnS03  +  Na2S2G4  x  H20. 

Milk  of  lime  is  then  added  to  precipitate  ZnO  and  CaS03,  and  the  liquor 
is  saturated  with  salt  at  50°,  and  cooled  to  crystallise  the  hyposulphite. 
By  adding  excess  of  caustic  soda  to  a  cone,  solution  of  the  crystals  at  50°, 
the  anhydrous  salt  is  precipitated  as  a  powder,  which  may  be  filtered 
and  washed  with  alcohol.  Various  hyposulphite  preparations  containing 
aldehydes,  zinc  compounds  (Rongalite),  etc.,  are  on  the  market,  which 
are  more  stable. 

Ammonium  Sulphite. — S02  from  a  siphon  is  passed  in  a  vigorous  stream 
into  2  parts  of  cone,  ammonia  solution  (D.  0-880)  and  1  part  of  ice,  sur- 
rounded by  a  freezing  mixture.  The  solution  gradually  assumes  a  light- 
yellow  colour.  When  no  more  S02  is  absorbed  the  solution  is  neutralised 
with  cone,  ammonia  solution.  This  solution  is  a  saturated  solution  of 
ammonium  sulphite  and  sometimes  deposits  crystals  on  standing. 

Sodium  Sulphide  (Na2S). — Evaluation. — The  crystalline  variety  is 
Na2S.9H20. 

5  gms.  sodium  sulphide  is  dissolved  in  water  up  to  250  c.cs.  and  care- 
fully neutralised  with  dilute  acetic  acid  in  presence  of  phenolphthalein 
until  the  latter  is  colourless.  A  -JN  solution  of  crystallised  zinc  sulphate 
(57-514  gms.  ZnS04.7H20  per  litre)  is  run  in  from  a  burette  until  all  the 
soluble  sodium  sulphide  is  converted  into  zinc  sulphide.  A  cone,  solution 
of  cadmium  sulphate  is  spotted  on  thick  blotting-paper,  and  a  drop  of  the 
liquid  being  analysed  is  placed  near  it.  A  yellow  stain  will  be  produced 
as  long  as  any  soluble  sulphide  remains.  The  zinc  sulphate  is  added  until 
no  yellow  colour  is  given. 

Example. —       Volume  of  zinc  sulphate  -    9-3  c.cs. 

AT     a  •      OK  9'3   ><   0,078         A  i.M 

Na2S  m  25  c.cs.  =   =  0-1451  gm. 

%  Na2S  =  X510  X  100  =  29-02. 


INORGANIC  SECTION 


509 


Carbonyl  Chloride  (Phosgene). — 100%  sulphuric  acid,  to  which  is  added 
2%  dry  ignited  kieselguhr,  is  placed  in  a  flask  which  is  attached  to  a  small 
reflux  condenser  and  a  dropping  funnel.  Carbon  tetrachloride  is  placed 
in  the  funnel,  and  from  the  top  of  the  condenser  is  led  a  delivery  tube 
passing  through  an  empty  wash-bottle,  and  then  under  the  surface  of 
toluene  contained  in  a  Buchner  flask,  the  side  tube  of  which  is  led  to  a 
draught  duct.  The  sulphuric  acid  is  heated  to  140°,  when  the  carbon 
tetrachloride  is  allowed  to  drop  slowly.  After  the  reaction  commences 
the  temperature  may  be  lowered  to  about  120°,  and  this  temperature 
maintained  by  gentle  heat.  The  carbonyl  chloride  passes  over  and  is 
absorbed  in  the  toluene,  while  the  hydrogen  chloride  which  is  formed 
passes  over.  The  whole  operation  should  be  conducted  in  a  good  draught 
chamber  as  phosgene  is  very  poisonous. 

2H2S04  +  3CC14  —>  3C0C12  +  4HC1  +  S205C12. 

Nitrous  Fumes. — Arsenious  acid  (As203)  is  broken  into  small  pieces  and 
placed  in  a  flask  with  a  two-holed  cork,  which  carries  a  dropping  funnel 
and  a  delivery  tube.  The  delivery  tube  is  connected  to  an  empty  wash- 
bottle  surrounded  by  cold  water  to  condense  any  nitric  acid  which  passes 
over.  Nitric  acid  (D.  1-3)  is  dropped  in  gradually  from  the  funnel,  while 
the  flask  is  gently  heated  ;  a  stream  of  nitrous  fumes  is  readily  evolved. 

Chromic  Anhydride  (Cr03). — 1'5  vols,  of  cone,  sulphuric  acid  is 
added  gradually,  and  with  shaking  to  1  vol.  of  a  saturated  solution  of 
potassium  chromate.  The  mixture  is  allowed  to  cool,  when  the  anhy- 
dride separates  out  as  scarlet  crystals.  The  crystals  are  filtered  off, 
washed  with  a  little  nitric  acid,  and  dried  in  a  desiccator.  The  crystals 
are  hygroscopic,  and  should  be  preserved  in  a  well  stoppered  bottle. 

K2Cr04  +  H2S04  =  K2S04  +  Cr03  +  H20. 

Chromyl  Chloride  (Cr02Cl2). — A  mixture  of  4  parts  sodium  chloride. 
5  parts  potassium  dichromate  and  9  parts  fuming  sulphuric  acid,  is 
placed  in  a  retort  and  distilled  until  coloured  liquid  no  longer  passes  over. 
The  chromyl  chloride  is  then  redistilled  (B.P.  116°). 

K2Cr207  +  4NaCl  +  3H2S04.S03  =  2Cr02Cl2  +  2KHS04  +  4NaHS04. 


Specific  Gravities  and  Concentrations  op  Aqueous  Acid  Solutions. 


Hydrochloric. 

Nitric. 

Sulphuric. 

Acetic. 

% 

D.15 

% 

D.  15 

% 

D.  is 

% 

D.  15 

0-15 

1-005 

1-000 

1-005 

4-49 

1-030 

1-0 

1-0007 

2-14 

1-010 

1-90 

1-010 

10-19 

1-070 

5 

1-0067 

3-12 

1-015 

2-80 

1-015 

15-71 

1-110 

10 

1-0142 

4-13 

1-020 

3-70 

1-020 

20-91 

1-150 

15 

1-0214 

5-15 

1-025 

4-60 

1-025 

26-04 

1-190 

20 

1-0284 

6-15 

1-030 

5-50 

1-030 

31-11 

1-230 

25 

1  0350 

510 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Specific  Gravities  and  Concentrations  of  Aqueous 
Acid  Solutions — continued. 


Hydrochloric. 

Nitric. 

Sulphuric. 

Acetic. 

% 

D.15 

% 

D.is 

% 

D.15 

% 

D.15 

715 

1-035 

6-38 

1-035 

35-71 

1-270 

30 

1-0412 

8-16 

1-040 

7-26 

1-040 

40-35 

1-310 

35 

1-0470 

9-16 

1-045 

8-99 

1-050 

44-82 

1-350 

40 

1-0523 

10-17 

1-050 

9-84 

1-055 

50-11 

1-400 

45 

1-0571 

11-18 

1-055 

10-68 

1-060 

55-03 

1-450 

50 

1-0615 

12-19 

1-060 

11-51 

1-065 

60-65 

1-510 

55 

1-0653 

13-19 

1-065 

12-33 

1-070 

65-08 

1-560 

60 

1-0685 

14-17 

1-070 

13-95 

1-080 

70-32 

1-620 

65 

1-0712 

15-16 

1-075 

15-53 

1-090 

75-42 

1-680 

70 

1-0733 

16-15 

1-080 

17-11 

1-100 

80-68 

1-740 

75 

1-0746 

17-13 

1-085 

18-67 

1-110 

85-70 

1-790 

80 

1-0748 

18-11 

1-090 

22-30 

1-120 

90-05 

1-820 

85 

1-0739 

19-06 

1-095 

22-54 

1-135 

90-40 

1-822 

90 

10713 

20-01 

1-100 

24-08 

1-145 

91-00 

1-825 

91 

1-0705 

20-97 

1-105 

26-36 

1-160 

91-50 

1-827 

92 

1-0696 

21-92 

1-110 

28-63 

1-175 

92-10 

1-830 

93 

1-0680 

22-86 

1-115 

31-30 

1-185 

92-52 

1-832 

94 

1-0674 

23-82 

1-120 

32-36 

1-200 

93-05 

1-834 

95 

1-0660 

24-78 

1-125 

34-55 

1-215 

93-43 

1-835 

96 

1-0644 

25-75 

1-130 

36-78 

1-230 

94-20 

1-837 

97 

1-0625 

26-70 

1-135 

39-05 

1-245 

94-60 

1-838 

98 

1-0604 

27-66 

1-140 

41-34 

1-260 

95-00 

1-839 

99 

1-0580 

28-61 

1145 

44-41 

1-280 

95-60 

1-840 

100 

1-0553 

29-57 

1-150 

46-72 

1-295 

95-95 

1-8405 

30-55 

1-155 

49-07 

1-310 

97-00 

1-8410 

31-52 

1-160 

52-37 

1-330 

97-70 

1-8415 

32-49 

1-165 

55-79 

1-350 

98-20 

1-8410 

33-46 

1-170 

58-48 

1-365 

98-70 

1-8405 

34-42 

1-175 

61-27 

1-380 

99-20 

1-8400 

35-39 

1-180 

63-23 

1-390 

99-45 

1-8395 

65-30 

1-400 

99-70 

1-8390 

67-50 

1-410 

99-95 

1-8385 

69-80 

1-420 

Specific  Gravities  and  Concentrations  of  Aqueous 
Alkaline  Solutions. 


Caustic  Soda. 


0-61 

2-  00 

3-  35 

4-  26 


D.15 


1-007 
1022 
1-036 
1-052 


Caustic  Potash. 

Ammonia. 

% 

D.15 

/o 

1 

1-009 

0-45 

0-998 

3 

1-025 

1-37 

0-994 

5 

1-041 

2-31 

0-990 

7 

1-058 

3-30 

0-986 

INORGANIC  SECTION 


511 


Specific  Gravities  and  Concentrations  of  Aqueous 
Alkaline  Solutions— continued. 


Caustic  Soda. 

Caustic  Potash. 

Ammonia. 

% 

D.15 

% 

% 

D.ir> 

5-87 

1-067 

9 

1-074 

4-30 

0-982 

6-55 

1-075 

11 

1-092 

5-30 

0-978 

7-31 

1-083 

13 

1-110 

6-30 

0-974 

8-68 

1-100 

15 

1-128 

7-31 

0-970 

9-42 

1-108 

17 

1146 

8-33 

0-966 

10-97 

1-125 

19 

1-166 

9-35 

0-962 

12-64 

1-142 

21 

1-188 

10-47 

0-958 

14-37 

1-162 

23 

1-209 

11-60 

0-954 

15-91 

1-180 

25 

1-230 

12-74 

0-950 

16-77 

1-190 

27 

1-252 

13-88 

0-946 

17-67 

1-200 

29 

1-276 

14-46 

0-944 

19-58 

1-220 

31 

1-300 

15-04 

0-942 

21-42 

1-241 

33 

1-324 

15-63 

0-940 

23-67 

1-263 

35 

1-349 

16-82 

0-936 

25-80 

1-285 

37 

1-374 

18-03 

0-932 

27-80 

1-308 

39 

1-400 

19-25 

0-928 

29-93 

1-332 

41 

1-425 

20-49 

0-924 

32-47 

1-357 

43 

1-450 

21-75 

0-920 

34-96 

1-383 

45 

1-475 

23  03 

0-916 

36-25 

1-397 

47 

1-499 

24-33 

0-912 

37-47 

1-410 

49 

1-525 

25-65 

0-908 

38-80 

1-424 

51 

1-552 

26-98 

0-904 

39-99 

1-438 

53 

1-578 

28-33 

0-900 

41-41 

1-453 

55 

1-604 

29-69 

0-896 

42-83 

1-468 

57 

1-630 

30-37 

0-894 

44-38 

1-483 

59 

1-655 

31-75 

0-890 

46-15 

1-498 

61 

1-681 

32-50 

0-888 

47-60 

1-514 

63 

1-705 

33-25 

0-886 

49-02 

1-530 

65 

1-729 

34-95 

0-882 

67 

1-754 

69 

1-780 

Vapour  Pressures. 


Vapour  pressure  of  water  at  different  temperatures. 


Temperature. 

Pressure. 

Temperature. 

Pressure. 

Tempera- 
ture. 

40  gms.KOH: 
100c.c.H2O. 

49  gms.KOH: 
lOOc.c.  H20. 

mms. 

mms. 

mms. 

mms. 

0° 

4-6 

16° 

13-5 

10° 

6-5 

5-6 

2° 

5-3 

18° 

15-4 

12° 

7-5 

6-5 

4° 

6-1 

20° 

17-4 

14° 

8-4 

7-3 

6° 

7-0 

22° 

19-7 

16° 

9-6 

8-3 

8° 

8-0 

24° 

22-2 

18° 

10-9 

9-5 

10° 

9-2 

26° 

25-0 

20° 

12-4 

10-8 

12° 

10-5 

28° 

281 

22° 

13-9 

12-1 

14° 

11-9 

30° 

31-6 

Vapour  pressure  of  cone.  KOH  solution  at 
different  temperatures. 


CHAPTER  XLIV 


TESTS  FOR  ORGANIC  ACIDS,  ALKALOIDS,  CARBOHYDRATES 

Tests  for  some  Organic  Acids — -  Group  I. — Calcium  salts  insoluble 
in  water,  therefore  precipitated  by  CaCl2  either  in  cold  or  on  boiling  : 
Oxalic,  tartaric,  citric,  malic. 

Group  II. — Iron  salts  insoluble  in  water,  therefore  precipitated  by 
Fe2Cl6  from  neutral  solutions  :  Benzoic,  succinic. 

Group  III. — Acids  not  precipitated  by  CaCl2  or  Fe2Cl6  in  the  cold  but 
precipitated  by  AgN03  from  neutral  solutions  :  Acetic,  formic,  hydro- 
cyanic, cyanic,  hydroferrocyanic,  hydroferricyanic,  sulphocyanic. 

Group  IV. — Acids  not  precipitated  by  foregoing  reagents  :  Salicylic 
hippuric,  stearic,  uric,  gallic,  tannic,  lactic. 


TABLE  I. 

Preliminary  Examination  of  Common  Organic  Acids. 


1.  Heat  solid  substance  in  test  tube. 

2.  Heat  solid  substance  with  cone.  H2SO4. 

(a)  No  charring. 

White    )  Oxalic, 
sublimate.  >  Benzoic. 

Acetic    )  Acetic, 
odour.    }  Formic. 

Irritating  -\ 

odour  and  (Succinic. 

white  j 
sublimate.  ' 
Odour  of  | 

bitter     [  Hydrocyanic, 
almonds,  j 

°IZJ.  }  salicylic. 

(b)  Immediate  charring,  i 

Odour  of  ) 

burnt      y  Tartaric. 

Sugar,  j 
Odour  of  \ 

burnt      -  Uric, 
feathers,  j 

Odour  of  ^ 

bitter     V  Hippuric. 
almonds.  / 

Blackens  \ 
after  a     I  Citric, 
time.  ) 

(a)  No  charring. 

|  Formic. 
CO  evolved,  j  Succinic. 

( Ferrocyanic. 

salts  formed )  ^amG- 

(b)  Charring 
at  once. 

Tartaric. 
Gallic. 

Tannic. 

(c)  Charring 
after  a  time 

Citric. 
Malic. 

Uric. 
Lactic. 

TABLE  II. 

Tests  in  Neutral  Solutions. 

To  neutral  solutions  add  : — 

j  White  precipitate /in  the  cold        .        .     •   .        .  Oxalic. 

P1  j  Do.  in  the  cold  on  standing       .        .  Tartaric. 

l^l2j  Do.  Ion  boiling   Citric. 

\  Do.  Ion  continued  boiling  .        .        .  Malic. 

512 


TESTS  FOR  ORGANIC  ACIDS,  ALKALOIDS,  ETC.  513 


TABLE  II. — Tests  in  Neutral  Solutions — continued. 


To  neutral  solution  add  : — 
/Buff  precipitate 
I  Brownish -red  precipitate 
Prussian  blue  precipitate 
Fe2Cl6     -  Blueblack  precipitate 
Violet  coloration  . 
Greenish-brown  coloration 
'Red  coloration 


( White  ppt.  insol.  in  HN03,  sol.  in  NH4OH 

Do.  do.  do. 

Do.  do.  insol. 

Orange  ppt.  sol.  in  NH4OH 
White  ppt.  sol.  in  HN03  and  NH40H 


AgNO; 


Do.  do.  do. 
Do.  do.  NH4OH  . 
Do.  do.  do. 

Do.  do.  do. 

Do.  do.  do. 
Do.         do.  do. 

Do.  reduced  to  metallic  silver 

Do.  decomposed  by  HN03 

Do.  sol.  in  NH4OH 


Benzoic. 
Succinic. 
Ferrocyanic. 
Tannic,  Gallic. 
Salicylic. 
Ferricyanic. 
Acetic,  Formic, 
SuTpho  cyanic. 
Hydrocyanic. 
Sulphocyanic. 
Ferrocyanic. 
Ferricyanic. 
Oxalic. 
Tartaric. 
Citric. 
Malic. 
Acetic. 
Benzoic. 
Succinic. 
Salicylic. 
Formic. 
Cyanic. 


Preparation  o£  Neutral  Solutions  of  Salts  ol  Organic  Acids. 


Soluble  acids  should  be  dissolved  in  water  and  treated 
solution  until  phenolplithalein  is  just  turned  pink. 


with  Na2C03 


Insoluble  acids  or  salts  are  treated  with  excess  of  Na2C03  solution. 


The 


excess  of  alkali  is  then  removed  by  addition  of  mineral  acids  until  neutral 
to  phenoiphthalein. 

Neutral  solutions  should  be  of  about  10%  concentration.  ^ 
Ammoniacal  silver  nitrate  solution  is  made  by  adding  ammonia  carefully 
to  a  solution  of  AgN03  until  the  precipitate  at  first  formed  is  just 
re  dissolved. 


GROUP  I. 


on  heating,  give  carbonates. 
H2S04,  on  heating,  usually  no 


Oxalic,;  COOH.COOH  +  2H20.—  White  crystalline  solid.  Loses  2H20 
at  100°,  /tjien  melts  and  sublimes  partly  with  decomposition,  giving  off 
C02  angH.COOH. 

Alkafcjbxalates  are  soluble  in  water. 

All  palates  are  insoluble  in  alcohol. 

Oxalates  of  alkalis  and  alkaline  earths, 
Othei/metallic  oxalates  give  oxides.  Cone. 
chaiMng  ;  CO  and  C02  evolved. 

Solutions  of  oxalates  give  with — 

1.  KaCl2,  white  precipitate — CaC204,  soluble  in  HCi  and  HN03,  almost 
insoMble  in  acetone  and  ammonia. 

2.  J?AgN03,  white  precipitate — Ag2C204,  soluble  in  HN03  and  ammonia. 
3j§KMn04  in  dilute  H2S04  solution,  decolorised  and  C02  given  off. 

S.0.C.  L  L 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Tartaric,  CHOH.COOH 

CHOH.COOH. 

Colourless  crystals.    M.P.  167°— 170°. 

Readily  soluble  in  water,  moderately  in  alcohol,  sparingly  in  ether. 
Alkali  tartrates  are  soluble  in  water. 
All  tartrates  insoluble  in  alcohol. 

On  heating,  charring  takes  place ;  burnt  sugar  smell,  and  acid  vapours 
evolved. 

Cone.  H2S04,  on  heating,  turns  brown  then  black,  and  acid  vapours 
evolved. 

Neutral  solutions  of  tartrates  give  with — 

1.  CaCl2,  white  precipitate — CaC4H406,  usually  only  after  vigorous 
shaking ;  soluble  in  HO,  HN03  and,  if  precipitate  has  not  assumed  the 
crystalline  form,  in  acetic  acid.  Soluble  also  in  cold  cone.  KOH  after 
washing.    Re-precipitated  on  boiling. 

2.  AgN03,  white  precipitate — Ag2C4H406,  soluble  in  HN03  and 
ammonia.  Precipitate  dissolved  in  minimum  quantity  of  ammonia, 
deposits  silver  mirror  on  gently  heating. 

3.  KC1,  white  precipitate — KC4H506,  soluble  in  mineral  acids  and  in 
alkalis,  insoluble  in  acetic  acid.  Precipitation  induced  by  stirring  or 
by  addition  of  alcohol. 

Citric,  CH2COOH 

I 

COHCOOH  +  H20 

I 

CH2COOH. 

Colourless  crystals;  M.P.  100°  (anhydrous  acid,  M.P.  153°);  readily 
soluble  in  water  and  alcohol,  sparingly  in  ether. 
Alkali  salts  soluble  in  water. 
Most  citrates  insoluble  in  alcohol. 

On  heating,  melts  and  gives  off  water  ;  no  smell  of  burnt  sugar. 
Cone.  H2S04,  on  heating,  gases  evolved ;  solution  becomes  yellow  and 
then  dark. 

Neutral  solutions  of  citrates  give  with — 

1.  CaCl2,  white  precipitate — Ca3(H6H507)2  on  boiling;  no  precipitate 
in  the  cold.    Precipitate  soluble  in  NH4Ci,  insoluble  in  KOH. 

2.  AgN03,  white  precipitate— Ag3C6H507,  soluble  in  ammonia.  No 
mirror  formed  as  in  tartrates. 

3.  KC1  gives  no  precipitate. 

4.  Ca(OH)2  on  boiling,  white  precipitate— Ca3(C6H507)2,  which  redis- 
solves  on  cooling. 

Malic,   CHOH(COOH)CH2COOH.— Colourless    deliquescent  needles; 
M.P.  100°  ;  readily  soluble  in  water,  moderately  in  alcohol  and  in  ether. 
Metallic  malates  mostly  soluble  in  water. 

On  heating  loses  water  and  is  converted  to  fumaric  and  maleic  acids. 
Cone.  H2S04,  on  heating,  turns  brown  ;  CO  and  C02  evolved. 


TESTS  FOR  ORGANIC  ACIDS,  ALKALOIDS,  ETC.  515 


Neutral  solutions  of  malates  give  with — 

1.  CaCl2,  white  precipitate — Ca.C4H405,  on  boiling  from  cone,  solutions ; 
precipitation  assisted  by  alcohol. 

2.  AgN03,  white  precipitate — Ag2C4H405,  turning  grey  on  boiling. 

3.  Ca(OH)2,  no  precipitate,  even  on  boiling. 

GROUP  II. 

Benzoic,  C6H5COOH. — White  needles  or  scales  ;  M.P.  121° :  sparingly 
soluble  in  cold,  fairly  readily  in  boiling  water  ;  readily  soluble  in  alcohol 
and  in  ether. 

Mostjbenzoates  soluble  in  water  ;  all  give  benzoic  acid  with  mineral 
acids. 

On  heating,  melts  and  volatilises. 

On  heating  acid  or  salts  with  soda-lime,  benzene  evolved. 
Cone.  H2S04,  on  heating,  dissolves ;  no  charring ;  acid  precipitated  on 
dilution  with  water. 

Neutral  solutions  of  bsnzoates  give  with — 

1.  CaCl2,  no  precipitate  even  on  addition  of  alcohol. 

2.  Fe2Ci6,  buff  precipitate — Fe2(C7H502)6,  soluble  in  HClwith  liberation 
of  benzoic  acid. 

3.  HC1,  free  acid  precipitated. 

4.  BaCl2,  in  presence  of  ammonia ;  no  precipitate  even  on  addition  of 
alcohol. 

Succinic,  COOH.CH2CH2.COOH.  —  Colourless  prisms  ;   M.P.  181°  ; 
soluble  in  water,  sparingly  soluble  in  cold  alcohol  and  ether. 
On  heating,  loses  water,  yielding  anhydride. 
Succinates  char  at  high  temperature. 

Cone.  H2S04  added  to  succinates  ;  on  heating,  solution  turns  dark  and 
sublimate  forms  on  cold  part  of  dry  tube. 
Neutral  solutions  of  succinates  give  with — 

1.  CaCl2,  no  precipitate  even  on  boiling. 

2.  Fe2Cl6,  brownish  red  precipitate  ;  basic  ferric  succinate  easily  soluble 
in  HC1. 

3.  BaCl2  in  presence  of  ammonia,  white  precipitate  on  addition  of 
alcohol. 

GROUP  III. 

Formic,  H.COOH.— Colourless  liquid  ;  M.P.  8°  ;  B.P.  101°.  Pungent 
odour  ;  vapour  burns  with  blue  flame.  Miscible  in  all  proportions  with 
water,  alcohol  and  ether.  Most  formates  soluble  in  water,  sparingly 
soluble  in  alcohol. 

Formates,  when  heated,  evolve  CO  yielding  carbonates,  oxides  or  metals. 

Cone.  H2S04,  CO  evolved. 

Neutral  solutions  of  formates  give  with — 

1.  Fe2Cl6,  red  coloration,  which  on  boiling  yields  reddish  precipitate 
of  basic  ferric  formate. 

L  L  2 


516  SYSTEMATIC  ORGANIC  CHEMISTRY 


2.  AgN03  in  cone,  solutions,  white  precipitate  —  AgCH02,  turning 
dark  even  in  cold,  owing  to  deposition  of  metallic  silver.  This  decom- 
position of  silver  formate  does  not  take  place  in  presence  of  excess 
ammonia. 

3.  HgCl2,  on  warming,  white  precipitate  —  Hg2Cl2,  or  grey  precipitate 
of  metallic  mercury. 

4.  Solutions  of  formates  or  formic  acid  decolorise  permanganate 
solution. 

5.  Solutions  of  formates  or  formic  acid,  with  few  drops  alcohol  and 
few  drops  cone.  H2S04,  on  warming,  give  ethyl  formate,  recognised  by 
sweet  smell. 

Acetic,  CH3.COOH.  —  Colourless  crystals  ;  M.P.  17°  ;  B.P.  119°  : 
characteristic  odour  ;  vapour  burns  with  bluish  flame  ;  miscible  in  all 
proportions  with  water,  alcohol  and  ether. 

All  acetates,  except  silver  and  mercury  and  the  basic  acetates  of 
iron  and  aluminium,  are  soluble. 

Acetates,  when  heated,  give  acetone. 

Cone.  H2S04,  on  heating,  liberates  acetic  acid. 

Neutral  solutions  of  acetates  give  with — 

1.  Fe2Cl6,  red  coloration,  which  on  boiling  yields  brownish  precipitate 
of  basic  ferric  acetate.    The  red  colour  is  destroyed  by  HC1,  but  not  by 

2.  AgN03  in  cone,  solutions,  white  crystalline  precipitate — AgC2H302, 
soluble  in  hot  water  and  in  ammonia.  Silver  acetate  is  not  reduced  when 
the  solution  is  boiled. 

3.  Solid  acetates  with  cone.  H2S04  and  a  few  drops  of  alcohol,  on 
heating,  give  ethyl  acetate,  recognised  by  pleasant  odour. 

4.  Dry  acetates  mixed  with  a  trace  of  As203,  when  heated,  give  vapours 
of  cacodyl  oxide,  As2(CH3)40,  recognised  by  smell  (caution  !  vapours  are 
very  poisonous). 

Hydrocyanic,  HCN. — Colourless  volatile  liquid  ;  B.P.  26°  ;  burns  with 
reddish-violet  flame  ;  soluble  in  water,  alcohol  and  ether. 

Aqueous  solution  does  not  redden  blue  litmus.  Cyanides  of  the  alkali 
and  alkaline  earth  metals  soluble  in  water.  Most  other  metallic  cyanides 
insoluble. 

Cone.  H2S04,  on  heating,  liberates  CO. 

Dilute  HCi,  in  cold,  liberates  HCN,  recognised  by  smell  (caution  !). 
Solutions  of  cyanides  give  with — 

1.  AgN03,  white  precipitate  —  AgCN,  insoluble  in  dilute  HN03, 
soluble  in  ammonia  and  KCN  solution. 

2.  NaOH  with  few  drops  FeS04  and  Fe2Cl6  solutions,  acidified  with 
HCi,  precipitate  of  Prussian  blue. 

3.  Yellow  ammonium  sulphide,  on  evaporation  to  dryness,  thiocyanate, 
which  gives  with  Fe2Cl6  in  dilute  HCi,  deep  red  colour. 

Cyanic,  HCNOo — Unstable  liquid  ;  smell  similar  to  acetic  acid. 
Cyanates  with  HCI  give  C02  and  NH4C1. 


TESTS  FOR  ORGANIC  ACIDS,  ALKALOIDS,  ETC. 


517 


Aqueous  solution  of  KCNO  on  standing  gives  NH3,  leaving  K2C03  in 
,  solution. 

Solutions  of  cyanates  give  with  AgN03,  white  precipitate  —  AgCNO, 
soluble  in  ammonia  ;  decomposed  by  acids  with  liberation  of  C02  and 
formation  of  an  ammonium  salt. 

For  conversion  to  urea,  see  p.  429. 

Thiocyanic,  HONS.— Unstable  liquid  ;  salts  mostly  soluble  in  water, 
and  are  decomposed  when  heated. 

Solid  salts  heated  with  H2S04  yield  C02,  HCN  and  H2S. 
Solutions  of  thiocyanates  give  with — 

1.  AgN03,  white  precipitate — AgCNS,  insoluble  in  dilute  HN03, 
sparingly  soluble  in  ammonia  ;  also  soluble  in  KCNS. 

2.  Fe2Cl6  to  dilute  solution,  deep  red  coloration — Fe2(CNS)3,  colour  is 
unchanged  by  HC1,  but  destroyed  by  HgCl2. 

For  conversion  to  thiourea,  see  p.  428. 

Hydroferrocyanic,  H4Fe(CN)6.— Colourless  crystalline  solid,  readily 
soluble  in  water. 

Salts  of  alkali  and  alkaline  earth  metals  soluble  in  water. 
All  ferrocyanides  are  decomposed  by  heat. 
Cone.  H2S04,  on  heating,  CO  evolved. 
Solutions  of  ferrocyanides  give  with — ■ 

1.  Fe^Cl6,  dark  blue  precipitate — Prussian  blue,  Fe4{Fe(CN)6}3, 
insoluble  in  HC1,  soluble  in  oxalic  acid. 

2.  FeS04,  pale  blue  precipitate,  which  rapidly  darkens  on  exposure 
to  air. 

3.  AgN03,  white  precipitate — Ag4Fe(CN)6,  insoluble  in  dilute  HN03. 
and  in  ammonia,  soluble  in  KCN. 

4.  CuS04,  chocolate  precipitate — Cu2Fe(CN)6,  insoluble  in  dilute  acids. 

Hydroferricyanic,  H3Fe(CN)6. — Yellow  crystalline  solid,  readily  soluble 
in  water. 

All  metallic  ferricyanides  are  decomposed  by  heat. 
Cone.  H2S04,  on  heating,  CO  and  C02. 
Solutions  of  ferricyanides  give  with — 

1.  Fe2Cl6,  brown  or  dark  green  coloration. 

2.  FeS04,  dark  blue  precipitate— Turn  bull's  blue,  Fe3{Fe(CN)6}2, 
insoluble  in  acids,  decomposed  by  KOH. 

3.  CuS04,  greenish-yellow  precipitate — Cu3{Fe(CN)6}2. 

4.  AgN03,  orange  precipitate — Ag3Fe(CN)6,  insoluble  in  dilute  HN03, 
soluble  in  ammonia  and  KCN. 

GROUP  IV. 

Salicylic,  C6H4OH.COOH  [1.2].  —  Colourless  needles  ;  M.P.  157°  ; 
sparingly  soluble  in  cold,  moderately  in  hot  water  ;  easily  soluble  in 
alcohol  and  in  ether. 

Most  salicylates  are  soluble  in  water,  and  give  salicylic  acid  with 
mineral  acids.    When  strongly  heated  gives  C02  and  phenol.  Salicylic 


518  SYSTEMATIC  ORGANIC  CHEMISTRY 


acid  or  salicylates  mixed  with  soda-lime  and  heated  give  phenol,  recognised 
by  its  smell. 

\. '  The  acid  is  soluble  in  cone.  H2S04,  and  is  reprecipitated  on  dilution 
with  water. 

Neutral  solutions  of  salicylates  give  with — 

1.  Fe2Cl6,  violet  coloration  ;  colour  destroyed  by  acids  or  alkalis. 

2.  Bromine  water,  yellowish-white  precipitate. 

3.  Dry  salicylates,  with  few  drops  methyl  alcohol  and  cone.  H2S04, 
on  warming,  methyl  salicylate  (oil  of  winter  green)  ;  recognised  by  smell. 

Hippuric,  CH2NH.COC6H5COOH. — Colourless,  crystalline  substance  ; 
M.P.  187°  ;  readily  soluble  in  hot  water,  or  in  hot  alcohol ;  on  heating, 
benzonitrile  (odour  of  oil  of  almonds) ;  on  heating  with  soda-lime,  NH3 
evolved. 

Neutral  solutions  of  hippurates  give  with — 

1.  Dilute  acids,  hippuric  acid.  With  cone.  HC1  at  100°,  benzoic  acid 
separates,  leaving  glycine  in  solution. 

2.  Fe2Cl6,  brown  precipitate. 

Uric,  C5H4N403. — White  crystalline  powder  ;  sparingly  soluble  in  water 
and  all  solvents  ;  insoluble  in  cold  Na2C03,  but  soluble  in  NaOH.  On 
heating,  NH3,  HCNO,  HCN  and  urea  are  formed. 

Cone.  H2S04,  in  cold,  soluble  ;  on  heating,  C02  and  S02  evolved. 

The  Murexide  Test. — Evaporate  a  little  uric  acid  and  dilute  HN03  to 
dryness.  Add  few  drops  of  ammonia  to  the  red  residue  when  cold  ; 
purple  coloration.  Uric  acid  reduces  Fehling's  solution  on  prolonged 
boiling. 

Tannic  (Gallo-tannic),  C14H10O9  +  2H20.  —  Colourless,  amorphous, 
glistening  mass  ;  decomposes  on  heating  ;  very  soluble  in  hot  water. 
Can  be  "  salted  "  out  of  solution  by  NaCl. 
Tannates  are  sparingly  soluble  in  water. 
Action  of  caustic  alkalis  same  as  for  gallic  acid. 

Cone.  H2S04,  on  warming,  dark-green  coloration,  and  brownish-black 
precipitate  on  dilution. 

Neutral  solutions  of  tannates  give  with — 

1.  Fe2Cl6,  bluish-black  precipitate,  soluble  in  HC1,  but  reprecipitated 
by  ammonia. 

2.  KCN,  no  coloration. 

3.  Tartar  emetic,  precipitate. 

4.  Pb(CH3COO)2,  acidified  with  acetic  acid,  white  precipitate. 

5.  Gelatin,  greyish  precipitate. 

6.  AgN03,  metallic  silver. 

7.  NH4C1  and  ammonia,  precipitate. 

Gallic,  C6H2(OH)3COOH  [3.4.5.1].— Colourless,  silky  needles  ;  decom- 
poses on  heating,  giving  pyrogallol  and  leaving  charred  residue  ;  sparingly 
soluble  in  cold  water  ;  readily  soluble  in  hot  water,  and  in  alcohol. 

Most  gallates  are  sparingly  soluble  in  water,  and  when  mixed  with 
caustic  alkalis  oxidise  in  air,  giving  coloured  solutions. 


TESTS  FOR  ORGANIC  ACIDS,  ALKALOIDS,  ETC!. 


519 


Cone.  H2S04,  on  warming,  dark-red  solution,  and  dark-red  precipitate 
on  dilution  with  water. 

Neutral  solutions  of  gallates  give  with— 

1 .  Fe2Clg,  bluish-black  precipitate,  soluble  in  excess  to  a  green  solution. 
The  precipitate  is  also  soluble  in  HC1. 

2.  KCN,  pink  coloration,  which  disappears  on  standing. 

3.  Pb(CH3C00)2  acidified  with  acetic  acid,  no  precipitate. 

4.  Solution  of  gelatin,  no  precipitate. 

5.  Fehling's  solution,  precipitate  of  Cu20. 

6.  AgN03,  metallic  silver. 

7.  NH4C1  and  ammonia,  no  precipitate. 

Lactic,  CHg.CHOH.COOH. — Syrupy  liquid  ;  decomposes  on  heating, 
giving  acetaldehyde. 

Neutral  solutions  of  lactates  give  with — ■ 

1.  AgN03,  no  precipitate. 

2.  ZnS04,  zinc  salt  on  crystallising — star-shaped  groups. 

3.  CaCl2,  no  precipitate. 

4.  KMn04  acidified,  on  warming,  decoloration. 


Alkaloids 


Caffeine 

Quinine 

Cinchoninc 

Morphine 

Codeine 

Narcotine 

Strychnine 

Bruoine 

Nicotine 

Conine 

Atropine 


Common  Types. 

M.P.  234° 


B.P. 

m!p. 


Source. 

Tea,  coffee. 
179°  ) 

9^^0  j  Cinchona  bark. 
230°  \ 

155°  '  Opium. 
176°  ) 
268°  j 

168°  j  Strychnos  nux  vomica. 

247°  Tobacco. 

167°  Hemlock. 

115°    Deadly  nightshade. 


Most  of  the  alkaloids,  with  the  exception  of  conine  and  nicotine,  are 
crystalline  solids  ;  they  are  usually  insoluble  or  sparingly  soluble  in 
water,  but  being  nitrogen  bases  they  dissolve  in  acids,  forming  soluble 
salts,  from  which  the  base  is  precipitated  by  dilute  NaOH  or  Na2C03. 
The  majority  are  optically  active  and  possess  a  bitter  astringent  taste, 
as  well  as  an  extremely  poisonous  character. 

General  Tests. — 1.  Solution  of  iodine  in  KI — brown  amorphous  ppt. 

2.  Nessler's  solution — white  or  discoloured  amorphous  ppt. 

3.  Potassium  mercuric  iodide — white  or  yellowish- white  ppt. 

4.  Phosphomolybdic  acid — light  to  brownish-yellow  gelatinous  ppt. 

5.  Chloroplatinic  acid — yellow  crystalline  solid. 

6.  Tannic  acid  or  picric  acid  in  aqueous  solution — precipitates  almost 
all  the  alkaloids. 


520 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Separation  of  the  Alkaloids. — Geoup  I.— Precipitated  by  NaHC03. 
Morphine,  cinchonine,  quinine,  narcotine. 

Group  II.— Not  precipitated  by  NaHC03.    Strychnine,  brucine. 

Group  III. — Liquid  alkaloids,  volatile  in  steam.    Conine,  nicotine. 

Group  IV.— Alkaloids  not  contained  in  I.,  II.,  or  III.,  but  which  may 
be  extracted  from  alkaline  solution  by  an  organic  solvent  (CH.C13). 
Caffeine  (theine),  atropine,  codeine,  cocaine. 

GROUP  I. 

Morphine,  C17H1903N  +  H20.— White  amorphous  or  crystalline  sub- 
stance, sparingly  soluble  in  cold  water  and  in  ether  ;  M.P.  230°. 
To  colourless  solution  in  cone.  H2S04  add — 

1.  Cone.  H2S04  containing  a  few  drops  HN03 — A  violet  coloration  on 
standing. 

2.  Cone.  HN03 — Red  coloration,  changing  to  yellow  on  warming. 

3.  Crystal  of  K2Cr207 — Bright-green  coloration. 

4.  One  drop  of  formalin — Purple  colour,  changing  to  blue. 
To  aqueous  solution  of  salt  add — 

1.  NaOH — Base  precipitated,  soluble  in  excess. 

2.  Fe2Cl6  (neutral  solution) — Blue  coloration. 

3.  HI03  solution — Iodine  liberated,  test  with  starch. 

Cinchonine,  C19H22ON2. — White  powder  or  crystalline  compound  ; 
almost  insoluble  in  water  ;  c/-rotatory  ;  M.P.  255°. 
Solutions  of  salts  do  not  exhibit  fluorescence. 
Cone.  H2S04  dissolves  ;  becomes  brown  or  black  on  heating. 
To  aqueous  solution  of  salt  add — 

1.  NaOH — Base  precipitated,  insoluble  in  excess. 

2.  Chlorine  water,  and  then  a  few  drops  of  NH4OH — Light- yellow  ppt. 

3.  K4Fe(CN)6  to  neutral  or  slightly  acid  solution — Yellowish-white  ppt., 
soluble  in  excess  on  warming. 

Quinine,  C20H24O2N2  -f  3H20. — White  powder  (anhydrous)  or  crystal- 
line compound  ;  sparingly  soluble  in  water  ;  /-rotatory  ;  M.P.  177° 
(anhydrous)  or  67°  (hydrated).  Dilute  solutions  of  its  salts,  acidified 
with  H2S04,  exhibit  a  bluish  fluorescence,  which  is  discharged  by  HC1. 

Cone.  H2S04  dissolves  ;  turns  yellow  and  brown  on  heating. 

To  aqueous  solution  of  salt  add — 

1.  NaOH— white  ppt. 

2.  Cone,  chlorine  water  (J-  its  volume),  and  then  excess  of  cone.  NH4OH 
— Emerald  green  colour. 

3.  Chlorine  water,  K4Fe(CN)6  and  NH4OH — Red  coloration.  Quinine 
hydrochloride,  on  heating  alone,  assumes  a  violet  colour,  and  gives  off 
violet  vapours. 

Narcotine,  C22H2307N.— White  crystalline  powder ;  M.P.  176°  ; 
sparingly  soluble  in  hot  water,  soluble  in  hot  alcohol  and  in  ether  ;  salts 
react  acid  in  solution  ;  /-rotatory  in  neutral  solution,  (/-rotatory  in  acid 


TESTS  FOR  ORGANIC  ACIDS,  ALKALOIDS,  ETC.  521 


1.  Cone.  H2S04  on  warming,  colour  changes  from  blue- violet  to  red. 

2.  Dilute  H2S04  and  Mn(X,  on  heating  and  filtering,  opianic  acid 
(M.P.  150°)  separates. 

3.  Cone.  HN03  dissolves  to  yellow  solution,  turning  orange-red  on 
heating. 

4.  Cone.  H2S04  and  a  trace  of  HN03 — Turns  brown  and  then  red. 

5.  Cone.  H2S04  and  ammonium  molybdate — Green  coloration  changing 
to  red. 

To  a  solution  in  dilute  HC1  add — 

1.  NaOH — Base  precipitated,  insoluble  in  excess. 

2.  Chlorine  water  and  NH4OH — Yellow-red  colour. 

GROUP  II. 

Strychnine,  C21H2202N2. — Colourless  needles  ;  M.P.  268°  ;  sparingly 
soluble  in  water,  alcohol,  and  ether  ;  very  soluble  in  CHC13  ;  ^-rotatoiy 
in  alcohol. 

1.  Cone.  H2S04 — Colourless  solution  (even  at  100°)  which  gives  bluish- 
violet  to  red  with  oxidising  agents  (Pb02,  K2Cr207,  Mn02). 

2.  Cone.  HNO3 — Colourless  solution,  turning  yellow  on  heating. 
To  solution  of  salt  add — 

1.  NaOH — Base  precipitated,  soluble  in  excess  of  NH4OH. 

2.  K3Fe(CN)6  or  K2Cr04 — Yellow  crystalline  ppt.  in  neutral  and 
fairly  cone,  strychnine  salt  solution. 

Brucine,  C23H2604N2  +  4H20. — Colourless  needles  or  prisms  ;  M.P. 
168°  ;  sparingly  soluble  in  water,  readily  soluble  in  alcohol  and  in  chloro- 
form ;  [a]D  =  about  -  120°  (in  CHC13). 

1.  Cone.  H2S04 — Rose-red  coloration,  changing  to  yellow. 

2.  Cone.  HN03 — Rose-pink  coloration,  turning  yellow  on  heating,  and 
turning  to  purple  with  SnCl2. 

3.  Cone.  HC1,  followed  by  dilution  with  water  and  addition  of  chlorine 
water — Red  coloration,  turning  yellow  with  ammonia. 

To  solutions  of  its  salts  add — ■ 

1.  KOH — Base  precipitated,  insoluble  in  excess. 

2.  Hg2(N03)2,  to  a  neutral  solution — Crimson  colour  on  boiling. 

GROUP  III. 

Conine,  C8H17N. — Colourless,  oily  liquid,  turning  brown  on  exposure 
to  air  ;  volatile  in  steam  ;  B.P.  167°  ;  readily  soluble  in  water  and 
organic  solvents  ;  (^-rotatory. 

1.  Cone.  H2S04 — Purple,  and  then  an  olive  coloration. 

2.  Cone.  HN03 — Blood-red  coloration. 

3.  Phenolphthalein — Turned  pink  in  50%  alcoholic  solution,  colour 
intensified  by  addition  of  a  few  drops  CHC13. 

4.  After  standing  for  5  minutes  with  alcoholic  CS2,  the  mixture  gives 
a  brown  ppt.  with  a  drop  of  very  dilute  CuS04. 

5.  Albumen — Coagulated. 


522 


SYSTEMATIC  ORGANIC  CHEMISTRY 


Nicotine,  C10H14N2. — Colourless,  oily  liquid,  turning  brown  on  exposure 
to  air  ;  volatile  in  steam  ;  B.P.  247°  ;  readily  soluble  in  water  and 
organic  solvents  ;  /-rotatory. 

1.  Cone.  HC1 — A  light- violet  or  brown  coloration  on  warming,  changing 
to  orange  with  cone.  HN03. 

2.  Cone.  HN03 — Red  coloration. 

3.  Phenolphthalein — Only  coloured  pink  in  very  dilute  alcohol. 

4.  Albumen — Not  coagulated. 

5.  On  warming  1  drop  with  2  c.cs.  epichlorhydrin  gives  a  red  colour. 
To  solution  of  salt  add — 

1.  Iodine  in  KI — Yellow  precipitate  disappearing  after  a  time. 

2.  NaOH — Base  liberated,  but  not  precipitated. 

GROUP  IV. 

Caffeine  (Theine),  C8H10N4O2  +  H20.— Colourless  needles  ;  M.P.  234° ; 
sparingly  soluble  in  cold  water  and  in  alcohol,  readily  soluble  in  chloro- 
form ;  sublimes  unchanged. 

1.  Cone.  NaOH — Decomposed  and  methylamine  evolved. 

2.  Murexide  test — Treat  with  a  crystal  of  KC103  and  a  few  drops  of 
HC1,  evaporate  to  dryness  ;  the  red  residue  turns  purple  with  ammonia. 

To  aqueous  solution  add — 

1.  AgN03 — No  precipitate. 

2.  Iodine  in  KI— A  precipitate  ;  M.P.  215°. 

3.  K4Fe(CN)6  and  HN03  (iron  free) — Yields  Prussian  blue  on  warming. 

Atropine,  C17H23N03. — Silky  needles  or  prisms  ;  M.P.  115°  ;  very 
sparingly  soluble  in  water,  fairly  soluble  in  ether  or  benzene,  readily  in 
alcohol  or  chloroform  ;  optically  inactive. 

1.  Cone.  HN03 — Boiled  and  evaporated  to  dryness,  and  residue  treated 
with  alcoholic  potash  ;  yields  violet  colour,  changing  to  red. 

2.  Bromine  in  HBr — Yellow  crystalline  precipitate. 

3.  Baryta  water  on  evaporation  to  dryness — Odour  of  hawthorn 
blossom. 

4.  On  heating  to  108°  becomes  /-rotatory. 

Codeine,  C18H21N03. — Crystalline  compound  ;  M.P.  155°  ;  moderately 
soluble  in  water,  readily  in  alcohol  or  CHC13,  insoluble  in  petroleum 
ether  ;  /-rotatory. 

1.  H2S04,  followed  by  addition  of  a  crystal  of  FeS04 — Blue  colour. 

2.  FeCl3— No  colour. 

3.  NaOH— Base  insoluble.    Hydrochloride  ;  M.P.  264°. 

Cocaine,  C17H21N04. — Colourless  prisms  ;  M.P.  98°  ;  slightly  soluble 
in  water,  readily  in  organic  solvents  ;  /-rotatory. 

1.  Cone.  H2S04  and  a  few  drops  of  alcohol — Characteristic  odour  of 
ethyl  benzoate. 

2.  Acids  or  alkalis  (on  heating) — Yields  benzoic  acid  and  ecgonine 
(M.P.  205°). 

3.  KMn04 — Violet  precipitate. 


TESTS  FOR  ORGANIC  ACIDS,  ALKALOIDS,  ETC. 


523 


4.  K2Cr04  in  presence  of  HC1— Yellow  precipitate. 

5.  Aqueous  iodine  on  solutions  of  salts  yields — per-iodide,  M.P.  161°; 
hydrochloride,  M.P.  182°. 

Carbohydrates 

The  carbohydrates  are  crystalline  or  amorphous  solids  which  char  on 
heating,  and  emit  an  odour  of  burnt  sugar.  They  are  non- volatile. 
Some  are  soluble  in  water,  e.g.,  sugars  ;  some  are  insoluble,  e.g.,  cellulose. 

General  Test  for  Soluble  Carbohydrates. — To  a  dilute  solution  of  the 
carbohydrate  in  water  2 — 3  drops  of  a  saturated  alcoholic  solution  of 
a-naphthol  is  added,  and  2  c.cs.  of  cone,  sulphuric  acid.  A  violet  colora- 
tion is  produced,  which  is  discharged  by  alkali. 

Monosaccharoses. — (a)  Pentoses,  C5H10O5. — (1).  1 — 2  gms.  of  the  carbo- 
hydrate is  distilled  with  10  c.cs.  water  and  5  c.cs.  cone.  HC1 ;  the  distillate 
contains  furfurol,  which  gives  a  deep-red  coloration  on  addition  of  a  few 
drops  of  aniline  and  cone.  HC1. 

(2).  A  deep-red  colour  is  produced  on  heating  with  phloroglucinol  and 
cone.  HC1. 

Example. — Arabinose.  M.P.  160°  ;  [a]^8  =  +  105°  ;  reduces  Fehling's 
solution  ;  osazone,  M.P.  157°. 

(b)  Hexoses,  C6H1206. — (1).  Aldoses,  which  are  identified  by  heating  a 
small  amount  at  60° — 70°  with  10  c.cs.  of  bromine  water,  boiling  of  the 
excess  of  bromine,  and  adding  a  little  very  dilute  ferric  chloride  solution, 
when  a  deep-yellow  coloration  (due  to  the  presence  of  a  hydroxy  acid)  is 
produced. 

Example. — d-Glucose  (Grape  Sugar  or  Dextrose).  M.P.  146°  ;  [a]^0  — 
+  52-6.  Reduces  Fehling's  solution  and  ammoniacal  silver  nitrate ; 
osazone,  M.P.  205°  ;  oxime,  M.P.  137°. 

(2).  Ketoses,  which  may  be  identified  by  warming  1  part  with  0-5  part 
resorcinol,  and  a  little  dilute  HC1  when  a  red  coloration  is  produced, 
turning  to  a  brown  precipitate  ;  soluble  in  alcohol. 

Example. — d-Fructose  (Fruit  Sugar  or  Levulose).  M.P.  95°;  [a]^0  = 
—  95°  ;  reduces  Fehling's  solution  and  ammoniacal  silver  nitrate  ;  osazone 
M.P.  204°  ;  oxime,  M.P.  118°. 

Disaccharoses,  C12H22011. — On  hydrolysis  by  boiling  with  dilute  acids 
yield  monosaccharoses,  usually  hexoses. 

Examples. — (a)  Sucrose  (Cane  Sugar  or  Saccharose).  Colourless 
crystals  ;  M.P.  160°  ;  [a]!?  =  66-5°  ;  does  not  reduce  Fehling's  solution  ; 
does  not  form  an  osazone  ;  yields  invert  sugar  [a]^0  =  —  37-4°  on 
boiling  with  dilute  acids  ;  (osazone  of  invert  sugar  melts  at  204°)  . 

(b)  Maltose  (Malt  Sugar).  Hard,  white  crystals  ;  decomposes  on 
heating  ;  [a]|?  =  +  137°  ;  reduces  Fehling's  solution  and  ammoniacal 
silver  nitrate  ;  osazone,  M.P.  206°. 

(c)  Lactose  (Milk  Sugar).  Hard,  rhombic  prisms  ;  M.P.  205°  ;  [a]f?  = 
+  52-5°  ;    readily  reduces  Fehling's  solution  and  ammoniacal  silver 


524  SYSTEMATIC  ORGANIC  CHEMISTRY 


nitrate  ;  is  much  less  sweet  than  cane  sugar,  and  also  much  less  soluble 
in  water  ;  osazone,  M.P.  200°. 

Polysaccharoses,  (C6H10O5)w. — Amorphous,  tasteless  solids,  insoluble 
in  alcohol  and  in  ether  ;  a  few  are  soluble  in  cold  water  ;  on  hydrolysis 
with  dilute  acids  they  yield  carbohydrates  of  simpler  constitution. 

Example. — Starch.  Fine,  white  powder,  which  shows  an  organised 
structure  under  microscope  ;  insoluble  in  cold  water,  but  on  boiling 
yields  a  gelatinous  opalescent  solution  ;  aqueous  solution  yields  a 
characteristic  blue  colour  with  iodine  ;  solution  also  yields  precipitates 
with  tannin,  and  with  basic  lead  acetate  ;  does  not  reduce  Fehling's 
solution  or  ammoniacal  silver  nitrate.  On  heating  to  about  200°,  yields 
dextrin. 

ADDENDUM 
Preparation  of  Alcoholic  Potash 

Method  I. — 10  gms.  of  caustic  .potash  sticks  are  dissolved^  in  an  equal 
quantity  of  water  and  diluted  with  absolute  alcohol  to  400  c.cs.  ~  The  solution 
is  agitated  with  10  gms.  of  anhydrous  sodium  sulphate  until  clarified,  after 
which  the  clear  solution  is  decanted. 

Method  II. — 15  gms.  of  caustic  potash  sticks  are  agitated  with  500  c.cs.  of 
95  %  alcohol  at  ordinary  temperature  until  dissolved.  After  settling,  the 
clear  solution  is  decanted. 

When  preparing  the  solution  for  analytical  purposes,  caustic  potash 
"  purified  from  alcohol  "  should  be  employed.  The  solution  is  standardised 
with  hydrochloric  acid,  using  phenolphthalein  as  indicator. 


INDEX 


A 

Absorbents,  33 

for  water,  441 
Absorption    (apparatus    for  carbon 

dioxide),  442 
Accidents,  1 

Acetaldehyde,  408,  410,  426 
Acetaldehyde -ammonia,  300 
Acetamide,  292,  293 
Acetanilide,  296 

Aceto-acetic  ester,  132,  143,  153,  187, 
188 

Acet-p-chloranilide,  335 
Acetic  acid,  234,  241 
tests  for,  513,  516 
I  Acetic  anhydride,  258 
j  Acetone,.  96,  88 

(estimation  of),  494 
j  Acetone-cyanhydrin,  151 
I  Acetone-etbyl-mercaptol,  388 
Acetone-plienylhydrazone,  283 
/Acetone-semicarbazone,  285 
j  Acetonitrile,  407 
Acetonyl-acetone,  188 
Acetophenone,  82,  84 
Acetophenone-oxime,  280 
\  (transformation  of),  282 
Acetyl 

chloride,  324 

groups  (estimation  of),  476 
Acetylene,  166 
Acetylides,  115 
Acetyl-mesitylene,  83 
Acid  solutions  (specific  gravities  and 

concentrations),  509 
Acrolein,  407 

Acyl  groups  (estimation  of),  476 
Adams,  343,  417 
jAir  bath,  35 
^-Alanine.  395 

Alcoholic  potash,  235,  476,  524 
.Aldehydes  (estimation  of),  479 
Aldehyde-ammonia,  158 
Aldime,  100 
Aldol,  96 

condensation,  95 
Algol  Yellow,  384 
Alizarin,  193,  384 
Alizarin  Blue,  160 


Alkaline 

reduction,  355 

solutions  (specific  gravity  and  con- 
centration), 510 
Alkaloids  (tests  for),  512,  519 
'  Alkyl  bromides,  328 
Aluminium  chloride.  55,  58,  80,  115, 
498,  503 

Aluminium -mercury  couple,  55,  58, 

175,  503 
Amides,  292,  293 

(estimation  of),  479 
4-Amido-hydroxy-benzoic  acid,  354 
Amines  (estimation  of),  475,  489 
p -Amino -acetanilide,  354 
2-Amino-anthraquinone,  296 
Amino-azo-benzene,  418 
o-Amino-benzaldehyde,  163 
Amino  compounds,  350 
^-Amino-dimethyl-aniline,  380 
Amino -guani dine  derivatives,  285 
4-Amino-3-methyl-benzophenone,  156 
a-Amino-/3-naphthol,  359 
Amino-naphthol  disulphonic  acid,  307 
Amino -naphthol  sulphonic  acid,  314 
p -Amino -phenol,  203 
Amino -salicvlic  acid,  359 
Ammonia,  499,  503 
Ammonium  sulphite,  508 
Amyl  nitrite,  251 
Aniline,  350 

standard  solution,  488 

hydrochloride,  419 

hydroferrocyanide,  419 

nitrate,  419 

sulphate,  419 
Anils,  220 

Animal  charcoal,  30 
Anisole,  211 
Anthracene,  170 

(estimation  of),  494 

(purification  of),  171 
Anthracene  Brown,  385 
Anthranilic  acid,  241,  291 
AnthranoL  78,  79,  182 
Anthraquinone,  77,  226 

dyes,  384 
Anthraquinone-/3-sulphonic  acid,  307 
Antipyrine,  388 


526 


INDEX 


Apparatus   for   the   continuous  re- 
moval of  ether,.  22 

Arabinose,  523 

Arsanilic  acid,  387 

Asbestos,  29,  493 

Aspirin,  386 

Atropine  (tests  for),  522 

Aur amine,  375 

Autoclaves,  42 

Auxochrome,  275 

Azo  compounds,  355,  371 

Azo  dyes,  372 

(estimation  of),  485 

Azoxy  compounds,  355,  371 


B 

Bakelite,  66 
Baking  process,  311 
Ball  condenser,  31 
Barbitone,  388 

Barium  hydroxide  (standard).  472 

Baths,  35 

Beckmann 

thermometer,  467 

transformation,  281.  282 
Beilstein,  15 

Bell-iar  filtering  apparatus,  30 
Benzaldehyde,  219,  220,  224,  225,  391 

semicarbazone,  284 
Benzal-chloride,  343 
Benzal-malonic 

acid,  109 

ester,  138 
Benzamide,  223,  294,  415 
Benzanilide,  297 
Benzanthrone,  79 
Benz-anti-aldoxime,  281 
Benz-syn-aldoxime,  400 
Benzene-sulphinic  acid,  319,  414 
Benzene-sulphonic  acid,  303,  316,  475 
Benzene-sulphonyl-chloride,  416 
Benzhydrol,  180 
Benzil,  411 

Benzilic  acid,  105,  106 
Benzidine,  155,  356 

tetrazonium  solution,  366 
Benzoic  acid,  113,  178,  232,  237 

(tests  for),  513,  515 
Benzoic  anhydride,  260 
Benzoin,  97 
Benzo-nitrile,  149,  150 
Benzophenone,  82,  87 

chloride,  323 
£>-Benzoquinone,  229 

dichlorimide,  420 
Benzopurpurin,  373 
Benzoyl-acetone,  91 
Benzoyl-aceto-acetic  ester,  136 


o-Benzoyl-benzoic  acid,  115 
Benzoyl' chloride,  324,  348 
Benzoyl-p-toluidine,  297 
Benzpinacone,  66 
Benzyl-aceto -acetic  ester,  136 
Benzyl  alcohol,  178,  194 
Benzyl  -benzoate,  257 
Benzyl-brom-malonic  acid,  433 
Benzyl -chloride,  344 
Benzyl -cyanide,  147 
Benzyl -malonic  acid,  235 
Benzylidine-acetone,  93 
Benzylidine-acetophenone,  94 
Benzylidine-aniline,  299 
Bi-diphenylene  ethane,  51 
Bindschedler's  Green,  381 
Boiling  point 

(determination  of),  18,  19 

of  salt  solutions,  35 
Bomb  furnace,  40 
Borneol,  393 

Brilliant  yellow  paper,  501 
Brom -acetic  acid,  337 
n-Brom-allocinnamic  acid,  399,  411 
m-Brom-benzoic  acid,  345 
a-Brom-cinnamic  acid,  399,  411 
Bromine,  502 

j)-Brom-dimethyl  aniline,  347 
a-Brom-naphthalene,  346 
p-Bromophenol,  343 
Brom-succinic  acid,  337 
a-Brom-stearic  acid,  336 
o -Brom -toluene,  339 
Brucine  (tests  for),  521 
Bucherer,  152 
Buchner  funnel,  29 
Bumping,  19,  26 
Butyl  alcohol  (tertiary),  69 
Butyric  acid,  403 


C 

Caffeine,  394 

(tests  for),  522 
Calcium  phosphate  (use  of),  30 
Camphor-aldehyde,  90,  91 
Camphor -oxime,  280 
Camphor -quinone,  222 
d-Camphor-sulphonic  acid,  304 
Cane  sugar  (estimation  of),  496 
Cannizarro,  178 
Capillary  tube,  15 
Carbamide,  429 
Carbinol  base,  376,  377 
Carbon  to  carbon  (linking  of),  48 
Carbon 

(detection  of),  435 

disulphide,  1 


INDEX 


527 


Carbon  and  hydrogen  (estimation  of), 
438 

Carbonyl  chloride,  83,  509 
Carbohydrates  (tests  for),  512,  523 
o-Carboxy  -  phenamino  -  acetonitrile, 

153 
(Jarius,  458 
Carron  oil,  1 

Catalytic   preparations  (apparatus 

for),  46 
Catechol,  201 
Caustic  soda,  499 
Cautions,  1 

Cerium  dioxide,  225,  447 
Chlor-acetic  acid,  348 
Chloral,  348 
Chi  oral -for  mamide,  386 
Chloral -hydrate,  348 
Chloramiiie-T,  387 
Chloranil,  229,  336 
Chlor-benzene,  339,  342 
Chlorhy drins,  216 
Chlorine,  502 
Chlor-malonic  acid,  338 
Chlor-nitro -benzene,  158 
Chloroform,  427 

m-Chloro-j9-hydroxy-benzyl  alcohol, 
194 

Chlorosulphonic  acid,  309,  507 
jt?-Chlor-toluene,  339 
Chromic  anhydride,  509 
Chro  mo  gen,  275 
Chromophore,  275 
Chromyl  chloride,  224,  509 
Chryso'idine,  370,  373,  374 
Cinchona  bark,  394 
Cinchonine  (tests  for),  520 
Cinnamic  acid,  107,  109 
Cinnamic  acid-dibromide,  332 
Cinnamic -aldehyde,  93 
Cinnamic -anhydride,  255 
Citraconic  acid,  236 
Citraconic-anhydride,  406 
Citric  acid  (tests  for),  513,  514 
Claisen  flask,  25 
Claisen,  90,  95,  140 
Cocaine  (tests  for),  522 
Codeine  (tests  for),  522 
Collidine,  404 
Collodion,  25 

Columns  (fractionating),  21 
Combustions,  438 
Combustion  of 

Carbon  and  hydrogen  (notes  on), 

j  446 

Volatile    and    hygroscopic  sub- 

1  stances,  447 
Cojmbustion  tube  and  furnace,  440 
Conant,  373 


|  Condenser  (air),  19 
!  Congo  red,  373 
paper,  501 

Conine  (tests  for),  521 

Constant  boiling  mixtures,  21,  22 

Continuous  steam  distillation,  24 

Control  tests,  23 

Cooling  mixtures,  10 
|  Copper-benzoyl-acetone,  92 

Copper 

bronze,  499 

powder,  60,  61,  239,  339,  504 

(reduced),  410 
Copper-zinc  couple,  175,  503 
|  Corks 

(boring  of),  7 

(softening  of),  7 
Corrected 

boiling  points,  20 

melting  points,  17. 
Corrections 

(boiling  point),  20 

(melting  point),  17 
Costing  (notes  on),  5 
Coupling,  275,  490 
Cresols,  199 
Croton-aldehyde,  93 
Crystallisation,  7 

(by  cooling),  8 

(by  evaporation),  11 
(special  methods),  12 

(fractional),  12 
Crystals  (separation  of),  11 
Gumming,  478 
Cupferron,  416 
Cuprous 

bromide,  504 

chloride,  339,  504 
Cyanhy  drins,  150 
Cyanic  acid  (tests  for),  513,  516 
Cyanogen,  222 
Cystine,  396 

D 

Decolorisation,  30 

(use  of  calcium  phosphate),  30 

(use  of  SG2),  30 
Decomposition  reactions,  403 
Dehydracetic  acid,  127 
Dehydrogenation  of  primary  alcohols, 

409 

Dehydrothiotoluidine,  318 
Denige's  reagent,  493 
Density  of  liquids,  43 
Desiccators,  11,  33 
Detection  of  elements,  435 
Diacet-o-toluidide,  298 
Diacetoxy-anthracene,  253 


528 


INDEX 


Diamino-anthraquinone,  384 
Diamino-stilbene    disulphonic  acid, 
354 

Diary  1 -methane  dyes,  374 
Diazoaminobenzene,  367 
Diazobenzene 

nitrate,  368 

perbromide,  369 

sulphate,  368 

sulphonic  acid,  433 
Diazomethane,  434 
Diazonium  compounds,  174,  275,  320, 
363,  365 

in  solution,  366 

(reactions  of),  369 

(stable),  366 
Diazotisation,  365 

(end  point),  365,  487 
Dibenzanilides,  156 
Dibenzyl,  51,  60 
2.6-Dibromaniline,  413 
Dibrom -succinic  acid,  346 
Dibrom-sulphanilic  acid,  342 
Dichlor-cinnamic  acid,  333 
Dichlor-nitraniline  (2.6.4),  335 
2.6-Dichlor-uric  acid,  325 
Dicyano-quinol,  154 
Dieithyl-acetal,  215 
Diethyl-acetosuccinate,  145 
Diethyl-adipate,  393 
Diethyl-aniline,  298 
Diethyl-collidine  dicarboxylate,  403 
Diethyl -dihydro  collidine  dicarboxyl- 
ate, 159 
Diethyl -ether,  208 
Diethyl-malonate,  251 
Diethyl-tartrate,  248,  250 
^p-^'-Dihydroxy-diphenyl,  200 
a-Diketones,  105,  221 
1.3-Diketones,  91 

Dimethyl  -  amino  -  azobenzene  sul- 
phate, 307 

Dimethyl-aniline,  298 

Dimethyl-benzophenone,  83 

Dimethyl-benzyl  -phenyl  -  ammonium 
chloride,  286 

Dimethyl -cellulose,  213 

Dimethyl -cyclohexenone,  77,  412 

Dimethvl-oxalate,  246 

Dimethyl-sulphate,  63,  64,  211,  254 

Dimethyl  terephthalate,  255 

Dimethyl-o-toluidine,  287 

a-a-Dinaphthol,  73 

^-^-Dinaphthol,  73 

^-/y-Dinaphthylamine,  430 

Dinitro -aniline,  diazonium  solution, 
367 

Dinitro-anthraquinone  (1.5  and  1.8), 
271 


|  2  :  4-Dinitro-benzaldehyde,  221 
1  m-Dinitro-benzene,  265 
I  2. 2,-Dinitro -benzidine,  271 

Dinitro -chlorbenzene,  266 

Dinitro -diphenyl,  158 

Dinitro -methylaniline,  261 

Dinitro -phenol,  198 

Dinitro -stilbene  disulphonic  acid,  314 

Dipentene,  412 

Dipentene -hydrochloride,  334 

Diphenyl,  48,  60,  61,  175 

Diphenyl-acetic  acid,  186 

Diphenylamine,  289,  290 

Di  phenyl -chloracetic  acid,  326 

Diphenyl -dihydro  anthracene,  57  . 

Diphenyl -disulphide,  421 

Diphenyl -iodonium  iodide,  421,  422 

Diphenylmethane,  52,  58,  172 

Diphenyl-methyl  ethylene,  62 

Disaccharoses,  223 

Disacryl,  407 

Distillation,  12,  18 
dry,  24 

fractional,  20,  26 

in  current  of  gas  or  under  reduced 
pressure,  27 

of  small  quantities,  19,  20 

steam,  22 

vacuum,  24 
Distribution  coefficient,  32 
Drugs,  386 
Drying  of 

liquids,  34 

solids,  33 
Dvfton,  22 
Dnlcitoi,  179 
Dumas,  450 
Dyes,  372 


E 

Elytrolytic  preparations,  391 
Eosin,  378 

Equivalent  of  a  base  (determination 
of),  474 

Equivalent  of  an  acid  (determination 

of),  472 
Esters  (estimation  of),  479 
Estimation  of 

acetone,  494 

acetyl  derivatives,  476 

acyl  derivatives,  476 

aldehydes,  479 

amides,  479 

amines,  489 

anthracene,  494 

azo  dyes,  485 

bromine  {Robertson),  461 


INDEX 


529 


Estimation  of — continued. 

carbon  and  hydrogen,  438 

chlorine  (Robertson),  461 

dye-leuco  compounds,  486 

enol-rnodification,  493 

esters,  479 

formaldehyde,  480 

glucose  and  cane  sugar,  496 
1    H  acid,  490 

halogens,  458 

halogens  and  sulphur  (simultane- 
ously), 464 
hydro  xyl  groups,  475 
metallic  radicles,  449 
methoxyl  and  ethoxyl  groups,  476 
nitro  compounds,  483 
nitrogen,  450,  455,  456 
nitroso  compounds,  484 
phenolic  compounds,  490 
^-phenylene-diamine,  492 
primary  and  secondary  amines,  475 
sulphur,  463 

thiophen  in  benzene,  493 
Etard,  224 
Ether,  208 

(apparatus  for  removal  of),  32 

(extraction  with),  32 

(purification  of).  209 
Ethers,  208 

Ethyl-acetate,  249,  254 
Ethyl-acetoacetic  ester,  135 
Ethyl-acrylate,  393 
Ethyl-alcohol  (purification  of),  206 
Ethyl-argento -cyanide,  290 
Ethyl-benzene,  59 
Ethyl-benzoate,  250 
Ethyl-bromide,  328 
Ethyl-chloride,  330 
Ethyl-cinnamate,  138 
Ethyl-cyanide,  147 
Ethyl-ether,  208 
Ethyl-iodide,  330 
Ethyl-hydrogen-tartrate,  247 
Ethyl-isocyanide,  290 
Ethyl-malonic  acid,  234 
Ethyl-malonic  ester,  132 
E^tyl-niercaptan,  321 
Ethyl -nitrate,  247 
Ethyl-nitrite,  274 
Ethyl-orthoformate,  210 
Ethyl -potassium  sulphate,  417 
Eth> lene,  406 
Eth-'^ne-dibromide,  332 
Eth^ne-dichloride,  334 
Eth^iene-dicyanide,  146 
Ethylene-glycol,  195 
Ethfylidene-bis-acetoacetic  ester,  139 
Extraction  of  solids,  31 
Extraction  with  ether,  32 

s.o.c. 


F 

I'Y.h  ling's  solution,  496 

Feist,  127 

Filter 

(hot  water),  10 

(steam  jacket),  10 
Filtration,  9,  28 
Filtration  of 

corrosive  liquids,  29 

small  quantities,  29 
Findlay,  45 
Fire  (cautions),  1 
Fischer,  164 
Fittig,  58,  65,  238 
Fluorescein,  378 

Formaldehyde  (estimation  of),  480 

Formamide,  293 

Formic  acid  (tests  for),  513,  515 

Fractional 

crystallisation,  12 

distillation,  20,  26 

liquefaction  and  evaporation,  176 
Fractionating  columns,  21 
Franldand-Duppa,  130 
Freezing  point  method  for  molecular 

weights,  466 

Friedel-Crafts,  54,  56,  80,  84,  115 
Friend,  13 
d-Fructose,  523 
Funnel 

(Buchner),  29 

(hot  water),  10 

(ice),  11 

(steam),  10 
Furfurol,  398 
Fusion  pot,  204 

Gallic  acid,  385 

tests  for,  513,  518 
Gattermann,  100,  150,  319,  339 
Gattermann-Koch,  85 
Geissler,  442 

a-d-Glucoheptonic  acid,  123 
a-Grlucoheptose,  184 
Gluconic  acid,  243 
Glucosamine  hydrochloride,  397 
Glucosazone,  283 
d-Glucose,  223,  523 

(estimation  of),  496 
Glutaric  acid,  413 
Glyceric  acid,  242 

(Pb  and  Ca  salts),  424 
Glycerol  (dehydration  of),  327 
Glycine,  431 

anhydride,  432 

M  M 


530 


INDEX 


Grlycocoll  ester,  432 
Grlycocoll -ester  hydrochloride,  395 
Glycollic  acid,  122,  195 
Grignard,  61,  62,  63,  67,  70,  89,  112 
"  128,  173 

reageni  (preparation  of),  68 


H 

H  acid,  307 

diazonium  solution,  367 

(estimation  of),  490 
Halogen  compounds,  175,  190 
Halogens 

(Beil stein's  test),  436 

carriers,  341 

(detection  of),  435 

(estimation  of),  458 
Hanizsch,  158 

Hard  glass  tubing  (cutting  of),  440 
Heating  under  pressure,  38 
Helianthin,  372 
Hexahydrobenzene,  167 
Hexahydrophenol,  169 
Hexamethylene  tetramine,  300 
Hints,  3 

Hippuric  acid  (tests  for),  518 

Hippuryl  chloride,  324 

Hofmann,  291 

Hydracetyl-acetone,  97 

Hydration  of  unsaturated  hydro- 
carbons, 426 

Hydrazines,  363 

Hydrazobenzene,  356 

Hydrazo -compounds,  355,  371 

Hydriodic  acid,  477,  498,  502 

Hydrobenzamide,  300 

Hydrobenzoin,  181 

Hydrobromic  acid,  502 

Hydrochloric  acid,  502 

Hydrocinnamic  acid,  185 

Hydrocyanic  acid  (tests  for),  513,  516 

Hydroferricyanic  acid  (tests  for),  513, 
517 

Hydroferrocyanic  acid  (tests  for),  513, 
517 

Hydrogen  compounds,  166 
Hydrogen  (detection  of),  435 
Hydrogenation  of  benzene,  168 
Hydroxy 

acids,  186 

aldehydes,  184 
Hydroxy -benzaldehyde,  99 
m-Hydroxy -benzoic  acid,  200 
o-Hydroxy-benzoic  acid,  111 
p-Hydroxy-benzoic  acid,  240 
o-  and  ^>-Hydroxy-benzyl  alcohols,  67 
Hydroxy  compounds,  65,  178,  193 


Hydroxy-oxy  compounds,  232 
Hydroxy -methylene-camphor,  90 
l-Hydroxy-4-naphthalene  sulphonic 

acid,  202 
Hydroxylamines,  363 
Hydroxyl  groups  (estimation  of),  475 


I 

Imides,  292,  293 
Indigo,  382 
Indoxyl,  383 

Inorganic  preparations,  502  et  seq. 
Iod-acetic  acid,  340 
2.4.1-Iod-nitraniline,  338 
Iodoform,  391,  428 
j9-Iod-toluene,  340 
/3-Iodo-propionic  acid,  326 
Iodosobenzene,  421 

acetate,  422 
Iodoxy-benzene,  422 
Ionone,  76 

(pseudo),  93 
Iron  filings,  499 
Irone,  76 
Iso-cyanides,  290 
Iso-nitroso  camphor,  222 
Iso-propyl  iodide,  190,  328 


K 

Ketenes,  127 
Ketimine,  103 

Keto-enol   tautomerism  (estimation 

of),  493 
Kjeldahl,  456 
Knecht  and  Hibbert,  486 
Knoevenegal,  152 
Kolbe,  110 
Kriiger,  76 


L 

Lactic  acid  (tests  for),  519 
Lactones,  184 
Lactose,  523  «< 
Lead  acetate  paper,  501 
Lead  peroxide,  504 

(evaluation  of),  504 
Lederer-Manasse,  66,  106 
Lens  (use  of),  13 
Leucine,  152 

Leuco  base,  376,  377,  383 
Leucyl -glycine,  288 
Lexicon  (Richter),  3 
Library  (use  of),  3 
Liebig,  95 


INDEX 


531 


Liquids,  inflammable  (distillation  of), 
19 

Litmus  i>aper,  500 
M 

Magenta,  375 
Malachite  Green,  377 
Malic  acid,  513,  514 
Malonic  acid,  119 
Maltose,  523 

Mandelic  acid  (resolution  of),  400 
Mandelonitrile,  151 
Mannitol-dibenzoate,  265 
Mannitol-hexacetate,  252 
Manometer,  25 
Mechanical  agitation,  37 
Melting  point 

(baths),  16 

(determination),  15 

(mixed),  17 

(of  alloys),  36 

tubes,  15 
Menthene,  411 
Menthyl  chloride,  327 
Merc  apt  ans,  321 
Mercuric  chloride,  84 
Mercury  vapour  lamp,  345 
Mesaconic  acid,  399 
Mesityl  oxide,  93 
i)[esitylene,  53 
Mesitylenic  acid,  238 
Metal  baths,  36 
Metallic  radicals 

(detection  of),  437 

(estimation  of),  449 
Metanilic  acid,  353 
Methane,  175 

w-Methoxy-resacetophenone,  104 
Methyl-alcohol,  392 

(purification  of),  206 
Methylamine  hydrochloride,  429 
Methyl -aniline,  287 
Methyl-benzoate,  254,  255 
Methyl -celluloses,  213 
Methyl -cyanide,  148 
Methyl-ethyl-acetic  acid,  188 
Methyl-ethyl-ketone,  187 
o-Methyl-glucoside,  214 
Methyl -hydrogen  succinate,  252 
Methyl-iodide,  330 
Methyl-ketol,  164 
Methyl- Orange,  372,  501 
Methyl -propyl -ketone,  187 
Methyl-Red,  372,  502 
Methyl -trinitro-benzoate,  256 
Methylene  Blue,  380 

'(zinc  free),  381 
Methylene-dimalonic  ester,  139 


Met  li.ylene  (irccn,  382 
Methylene-iodide,  191 
Michler's  ketone,  81 
Microscope  (use  of),  L3 
Miscellaneous  reactions,  415 
Mixed  acid,  262 

(analysis  of),  263 
Mixed  melting  points,  I  7 
Mixtures  (cooling),  10 
Molecular  weights  (determination  of), 

465 

Mono-brom-acetic  acid,  337 
Mono-brom-succinic  acid,  337 
Mono-chlor-acetic  acid,  348 
Mono-chlor-malonic  acid,  338 
Morphine  (tests  for),  520 
Mucic  acid,  244 

N 

/3-Naphthalene-sulpho -glycine,  423 
Naphthalene-/3-sulphonic  acid,  304 
Naphthalene -sulphonylchloride,  417 
Naphthalene  -1.4  -sulpho  -sulphinic 

acid,  319 
n-Naphthaquinone,  227,  230 
/3-Naphthaquinone,  230 
Naphthionic  acid,  312 
a -Naphthoic  acid,  233 
a-Naphthol,  202 
/3-Naphthol,  204 
Naphthol  Yellow  S,  379 
#-Naphthyl-acetate,  252 
a-Naphthylamine,  352 
/3-Naphthylamine,  295 
/^-Naphthyl-methyl-ether,  212 
Narcotine  (tests  for),  520 
Natural  sources  (products  from),  394 
Neutral  reduction,  363 
Nevile  and  Winther's  acid,  202 
Nickel  catalyst  (preparation  of),  167 
Nicotine  (tests  for),  522 
m-Nitraniline,  358 
^-Nitraniline,  268 

diazonium  solution,  367 
Nitration,  262 

(rules  of),  263 
Nitric  acid,  498 

fuming,  508 
Nitriles,  149,  150,  154,  232 
^p-Nitro-acetanilide,  268 
o-  and  j9-Nitro-anisole,  420 
m-Nitro-benzaldehyde,  270 
Nitrobenzene,  265,  273 

m-sulphonic  acid,  306 
o-Nitro-benzoyl  chloride,  325 
j9-Nitro -benzyl  bromide,  344 
Nitro  compounds,  261 

(isolation  of),  264 


532 


INDEX 


Nitro  dyes,  379 
Nitro -ethane,  274 

4-Nitro-3-hydroxy-benzoic  acid,  262 

Nitro -methane,  273 

Nitro -methylene  Blue,  382 

a -Nitro -naphthalene,  267 

/>- Nitro -phenetole,  355 

o-  and  ;p-Nitro -phenetole,  420 

o-  and  ^-Nitro -phenol,  270,  272 

p -Nitro  -phenylhydrazine,  363 

o  -Nitro -quinoline,  161 

ra-Nitro -salicylic  acid,  272 

o-  and  f  -Nitro -toluene,  266 

w-Nitro-toluidine,  269 

Nitrogen 

compounds,  146 

(detection  of),  433 

(estimation  of),  450,  456 
(notes  on),  455 
Nitroso -benzene,  418 
iso-Nitroso-camphor,  222 
Nitroso-compounds,  360 
^-Nitroso-dimethylaniline,  278,  380 
p -Nitroso -methylaniline,  278 
Nitroso -methylnrethane,  434 
Nitroso -p-naphthol,  277 
p-Nitroso -phenol,  277 
Nitrous  fumes,  271,  509 
Noyes  and  Warfel,  22 


0 

Oil  bath,  36 
Oleic  acid,  398 
Oleum,  305 

(estimation  of),  305 

of  given  strength,  306 
Orange  I.,  374 
Orange  II.,  374 
Organic  acids  (tests  for),  512 
Oxalic  acid,  237 

(anhydrous),  246 

(tests  for),  513 
Oxamide,  222 
Oxide  compounds,  208 
Oxide-oxy  compounds.  126,  246 
Oximes,  279,  360 

(Beckmann's    transformation  of), 
281,  282 
Oxy-compounds,  74,  219 
Oxy-  and  hydroxy-oxy-compounds, 

183 

Oxygen,  438,  447 


P 

Paracetaldehyde,  216,  427 
Paraldehyde,  216 


Para-rosaniline  hydrochloride,  376 
Perlan,  54,  107,  477 
Phenacetin,  389 
Phenanthraquinone,  227 
Phenazone,  388 
?>-Phenetidine,  355 
Phenetole,  209 
Phenol,  199,  204,  369 
Phenol-phthalein,  100,  500 
Phenols,  170 
Phenoquinone,  218 
Phenyl-acetic  acid,  $73 
r-Phenylalanine,  432 
Phenyl -benzo ate,  255 
#-Phenyl-/3-brompropionic  acid,  333 
Phenyl  diazonium  solution,  366 

(standard),  489 
Phenyl-dihydroxy -propionic  acid,  205 
a-Phenylethylamine,  14,  360 

carbamate,  362 

resolution  of,  401 
Phenyl -glycine,  430 
Phenyl-glycine-o-carboxylic  acid,  289, 

383,  431 
Phenyl-hydrazine,  364 
Phenyl -hydrazine -f>-sulphonic  acid, 

313 

Phenyl -hydrazone  of  ^-mannose,  420 
Phenyl-hydrazone  of  pyruvic  acid, 

283  \ 
Phenyl-hydrazones,  282  v 
Phenyl-hydroxylamine,  203,  363 
Phenyl  iodide  dichloride,  423 
Phenyl-isothiocyanate,  405 
Pheiiyl-methyl-carbinol,  68,  180 
l-Plienyl-3-methyl -pyrazolone,  284 
Phenyl-^-naphthylamine,  430 
Phenyl-sulpho -propionic  acid,  315 
m-Phenylene-diamine,  352 

sulphonic  acid,  313 
39-Phenylene- diamine,  353,  392 

(estimation  of),  492 
Phosgene,  509 
Phosphoric  acid,  498 
Phosphorous  (detection  of),  435 
Phosphorus 

di -iodide,  507 

trisulphide,  507 
Phthaleins,  100 
Phthalic  acid,  240 
iso-Phthalaldehyde,  225 
Phthalic  anhydride,  258 
Phthalimide,  279,  294 

potassium  salt,  420 
Picramic  acid,  358 
Picric  acid,  267 
Pinacoline  transformation,  74 
Pinacones,  50,  65,  74 
Piperic  acid,  108 


INDEX 


533 


Piperonyl  acrolein,  93 
Pirn  and  Scliiff,  460 
Platinichloride  of  bases,  474 
Poison  (cautions),  1 
Polari meter,  44 
Polysnlphides,  316 
Potash  bulbs,  442 
Potassium 

collidino-dicarboxylate,  235 

phthalimide,  420 

xanthate,  320 
Preparations  (lists  of),  4 
Primuline,  317,  382 
a-a-Propenyl-dichlorhydrin,  327 
Propenyl  tribromide,  341 
Propionic  acid,  112 
Pumps,  27 

Pyridine  methiodide,  286 
Pyrogallol,  403 

trimethyl  ether,  212 
Pyrone  and  phthalein  dyes,  378 
PyTonines,  101 
Pyruvic  acid,  408 


Q 

Quaternary  ammonium  compounds, 
286 

Quinaldine,  163,  164 
Quinhydrone,  181,  217,  218 
Quinine 

sulphate,  394 

(tests  for),  520 
Quinizarin,  102 
Quinol,  181,  200,  229,  418 
Quinoline,  160,  161,  163 
Quinones,  154,  170,  181,  227,  228 


K 

R-salt  (standard  solution),  489 
Baoult,  465,  466 

Reactions  (scheme  of  arrangement),  2 
Reagents  (approximate  concentration 
of),  500 

Receiver  for  distillation  in  a  current 

of  gas  or  under  reduced  pressure,  27 
Receivers  for  fractional  distillation, 

25,  26 
Reduction  in 

acid  solution.  350 

alkaline  solution,  355 

neutral  solution,  363 
Reduction  of 

jazo  compounds,  359 

pximes,  360 
Reflux  condenser,  206 


Eeformatsky,  128 
Reimer-Tiemann,  98,  117 
Beychler's  acid,  304 
Richter,  4,  15 
Robertson,  461 
Rubber  stoppers,  % ■>.,  25 


S 

8  abatier- Sender  ens ,  167 
Saccharic  acid,  243 
Saccharin,  309 
Salicylaldehyde,  99,  183 
Salicvlic  acid,  111 

(tests  for),  513,  517 
Salting  out,  30 
Sand  bath,  36 
Sandmeyer,  149,  273,  338 
Scheme  of  arrangement  of  reactions,  2 
Schiff's  azotometer,  451 
Sehmitt,  110 

Schotten-Baumami,  253,  296,  297 
Sealed  tubes,  38,  458 
Sealing  glass  tubes,  38,  40 
Seeding,  8,  9 
Semi-carbazones,  284 
Semi  dine,  155 
Semi-oxamazones,  285 
8 enter,  23 

Separating  funnels,  31 
Separation  by  extraction,  32 
Separation  of  immiscible  liquids,  31 
Setting-point,  17 
Silver 

nitrite,  505 

salt,  307 

salts  of  acids,  473 
Skraup,  159 
Smith,  22 

Sodamide,  91,  140,  506 
Sodium 

(granulated),  506 

(weighing  of),  505 
Sodium 

acetate  (anhydrous),  506 

amalgam,  505 

benzylate,  257 

bisulphite,  499,  506 

ethylate,  91.  505 

hypochlorite,  499,  508  * 

hyposulphite,  508 

nitrite,  498 

(standard  solution),  487 

press,  505 

residues,  2 

sulphide,  499 

(evaluation  of),  508 
Solution  (preparation  of),  9 


534 


INDEX 


Solvent  (selection  of),  8 
Soxhlet,  12,  31 

Specific  gravities  of  solutions,  509, 

510,  511 
Specific  rotation,  45 
Spotting,  489 
Sprengel  pyknometer,  44 
Stannous  chloride,  499 
Starch,  524 

iodide  paper,  501 
Steam 

distillation,  23,  351 
(continuous),  24 

(superheated),  23 
Stelzner,  15 

Stereochemical  reactions,  399 
Still-heads,  21 

Stoppers  (removing  fixed),  7 
Strecker,  152 

Strychnine  (tests  for),  521 
Sublimation,  28 
Succinic  acid,  119,  186 

(tests  for),  513,  515 
Succinic  anhydride,  259 
Succinimide,  292 
Sucrose,  523 
Sudan  dyes,  370 
Sulphanilic  acid,  31  lx 
Sulphinic  acids,  318 
Sulphonal,  388 

Sulphonation  apparatus,  38,  303 
Sulphone,  303,  322 
Sulphonic  acids,  302 

(isolation  of),  302 
Sulphonic  group  (reactions  of  ),  316 
Sulphur 

(detection  of),  435 

(estimation  of),  463 

monochloride,  327,  507 
Sulphuric  acid,  498 
Sulphuryl  chloride,  338 


T 

Tannic  acid  (tests  for),  513,  518 
Tartaric  acid  (tests  for),  513,  518 
Technical  products,  6 
Terephthalic  acid,  239 
Tertiary  butyl  alcohol,  69 
Test  papers,  500 
Tetra-brom-diphenylamine,  345 
Tetra-chlor-ethane,  117 
Tetra-methyl-diamino-di  phenyl  me 

thane,  375 
3  :  5  :  3'  :  5,-Tetramethy]-2-2/-di]i.v(h  - 

oxy-diphenyl  methane,  67 
o-^-o'-^Z-Tetra-nitro-diphenyl,  157 


Tetranitro -methane,  274 
Theine,  394 

(tests  for),  522 
Thermo-couple,  46 
Thermometers 

(choice  of),  15 

standardising,  17,  20 
Thianthren,  425 
Thiazine  dyes,  380 
Thiazole  paper,  501 
Thio -acetic  acid,  322 
Thio-carbanilide,  430 
Thio-cyanic  acid  (tests  for),,  513,  517 
Thio-diphenylamine,  317 
Thio -ethers,  \322 
Thionyl  chloride,  323 
Thiophen,  404 

(estimation  of),  493 
Thio -phenol,  424 

(Hg  and  Pb  salts),  424 
Thio -salicylic  acid,  320,  321 
Thio -urea,  428 
Thioxene,  405 
Tiemann,  76;  152 

Titanous  chloride  standard  solution, 

482,  499 
Titherley,  22. 
o-Tolidine,  357 

tetrazonium  solution,  366 
Toluene  bath,  35 
Toluene-o-sulphonamide,  310 
Toluene-^ -sulphonamide,  387 
o-  and  17-Toluene  sulphonic  acids,  3  04 

(separation  of),  305 
Toluene-o -sulphonyl    chloride.  305, 

309 

Toluene -sulphonyl    chloride,  3Cf5, 

387 

p-Toluic  acid,  233 

o-  and  ^-Toluidine,  351 

(separation  of),  351 
o-Toluidine  (separation  of  pure),  3£>2 
j9-Tomnitrile,  149,  150 
2 -j9-Toluoyl -benzoic  acid,  116 
p-Tolyl-aldehyde,  85 
Triaryl  methane  dyes,  324 
Tribrom-ethane,  195 
s-Tribromo  -benzene,  174 
Tribromophenol,  347 
Tribrom-s-xylenol,  347 
Tricarballylic  acid,  120 
Trichlorar 349 
Trimethy.  vse,  213 

Trimethyl-etliylene,  405 
Trimethyl-/3-naphthyl-ammonium 

iodide,  286 
Triphenyl- acetic  acid,  114 
Triphenyl-benzene,  54 
Triphenvl-carbinol,  70,  71,  193 


INDEX 


jTriphenyl-chlormethane,  425 
fTriphenyl-methane,  55,  173 
Tube 

capillary,  15 

furnace,  40 


U 

|  Ultra-violet  rays,  333 
Urea.  429 

Uric  acid  (tests  for),  518 
Uvitic  acid,  238 


V 

Vacuum  distillation,  24 
Vapour 

density  method,  465 

pressures,  511 
Veronal,  388 
Victor'  Meyer,  465 
Volhard,  429 


W 

Walker,  22 
Water 

baths,  35 

trap,  25 
Wurtz,  58 

X 

Xanthones,  126 
^-Xylene,  63 
s-Xylenol,  412 

Y 

Young,  22 

Z 

ZeiseL  476 
Zinc 

alkyl,  64,  71,  90 

ammonium  chloride,  503 

chloride  ( anhydrous ),  506 
Zinc -copper  couple,  175,  503 
Zinc  dust,  499 

(evaluation  of),  506 


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